What a wonderful mod. I had a blast playing it. I figured I'd drop in and share how my run went and my thoughts after playing.

I did default settings with qol mods. The super early game is a little jarring. I remember being annoyed at how the ore patch was mixed and the difficulty of expanding. But after I got over myself and I set up a red and green science I was enjoying myself. At this stage I was already sick of the mixed ore patches so I decided to set up an infinite ore loop. I remember at the start it was coin negative (or not coin positive enough to also sustain a 90spm base), but after a little of finagling I managed to generate iron/stone/copper to sell iron chests, stone furnaces and copper ore for coins. Then loop those back to generate more ore etc.

At this stage, the mod just became a infinite ore mod. I progressed all the way to space science with little interaction with the system (other then debugging my single coin loop). That isn't to say I didn't try. But every time I would look through the available trades I couldn't find a viable loop or method better than what I already had.

Once on fulgora, I got lucky with a iron ore (shipped on mass from nauvis) -> holmium -> coins recipe. Or I suppose, that's expected. Suddenly I was making gravity coins and all my work on Nauvis was basically chump change. I used that generator all the way to aquilo. Throughout this time, I completed quests and made a dedicated effort to level up my trades, but found the process tedious. And unrewarding (since I was still unable to find better loops than what I'd already found). I will mention that I somehow didn't do the productivity module upgrade for a long while so all I was getting was build distance or ammunition productivity.

Then aquilo. After the nonsense of jumpstarting the planet, I ventured out. Hoo, boy is aquilo unbalanced. Not only are trades massively overvalued (I tried importing solid fuel 100k at a time w/ 3 fast haulers which was good, but quickly found a cryo science to coins loop that blew that out of the water) but since there are so few items it is really easy to find 1 to 1 loops.

This is when the game sort of went off the rails. I randomly started moving with 2,000% movement speed. My bots had a cargo capacity of +17.8. Beacons were getting 300%+ bonus distribution efficiency. Trades went from 130% prod to 300+ in an hour or two. And I was mostly confused how it all happened. To be fair, it was late, but it took me a while to realize pressing the upgrade all trades button + all the the dungeons I was killing and using those hex cores had spiked all my numbers. It was trivial to get biolabs, beacons, and hex modules to red tier and set up a single biolab with 1.3e7% bonus speed. Couldn't feed the thing fast enough.

So yeah. Fun. I liked the dungeons, though was kinda sad they are all trivialized by a robust space fleet + artillery. The HV railgun is awesome. The red lightning is so freaking cool. So is the plague rocket, but the fact it doesn't kill buildings made me sad. I also don't really get the whole hex prism thing. The duplication ritual just seems like a whole lot of clicking to actually use the t1 cores. Thanks for making the mod. Below is some feedback.

1. The worst part by far of the mod is the constant zooming in and out and teleporting. This is mostly a symptom of my bad memory and having to buy, then sell. Then buy w/ 35 prod. Then electrocute an enemy. Then sell at 130 prod. Since you typically need two different hexes to do this it just takes a lot of frustrating teleporting around. What I really mean to say is that upgrading trades is really tedious. My suggestion then is to allow a feature for your robot network to complete a trade. For example, once hex ports are unlocked there is an additional button next to each trade that simply puts ghost items of the trade into the hex for your robot network to fulfill. This would allow you not to have to open and close so many windows to A) find a suitable trade B) go to the trade C) teleport there D) put the items inside (I made a logistics group with every item int eh game and still had to teleport back on every other trade to complete all the random items). This button upgrade could even be an aquilo unlock. I think its only really relevant late game when you are trying to get all items to be red.
2. Coin trades amounts are confusing on aquilo and for quality trades. 22 million gravity coins should be displayed as the corresponding amount of higher tier coinage.
3. I kind of feel like all trades that aren't 1 to 1 are a waste of time. Sure, in the early game you have to compromise, and even benefit from jumping through weird hoops, but even then you really want 3 to 1 at worst. Any unbalanced product is so difficult to deal with and sinks aren't a solution except in specific situations where you are only throwing away a small percentage of the profits. Basically what I'm saying is, that after the early game (up to space science) I never even considered any trade that had more than one input and one output. The bonus prod wasn't worth it. The idea I had for this is to make many more trades be 1 to 1, but then additionally modify the efficiency of trades based on location. That way, you are incentivized for shipping material long distance, and also there is a benefit to doing coin loops that aren't just item->coin->item->coin. Imagine if each planet has different random defaults so on one run you are shipping power poles to gleba, exporting barrels and exoskeletons from gleba to fulgora and fulgora converts all of those for maximum profit into coins. Or something.
4. The quantum bazaar should have a hotkey to buy 1 of the item on your cursor if you have it unlocked. So you can top up on inserters or whatever without having to open several windows.
5. Inventory size and walking speed should be capped or editable. I want 300-400% move speed. 2k% is too much. And my save is at that point where I can't selectively disable one of them since all of them give me 600+.
6. I don't get the point of strong boxes. It is kind of cute to get this tiny coin infusion every so often, but that's just it. The amount of coins is tiny. The number of laser turrets to get a strongbox passed level 30 is absurd. I mean the power requirement. I didn't bother using gun turrets. Anyway, I ignored them. Also, I found it hard to find them on the map. Maybe add a search feature/ping all strongboxes button?
7. A search feature for the catalogue would be appreciated. I ended up just selecting an item from the right most of the time.
8. I ended up using pentapod eggs summoned from the quantum bazaar to red star my aquilo trades. It was mildly annoying to wait fifteen minutes each time.
9. I never made a prometheum ship since I just bought the science.
10. coin generation is basically entirely dependent on how fast you can shove items in. What the items are is irrelevant. I think a more balanced game mode (that doesn't completely go off of the rails after 100 prod + belt stacking) would be to make any recipe that involves coins (buy or sell) not benefit from positive productivity (capped at 0%). This would mean that the minimum 'coin loop' would be coin->iron plate-> gears->coin. Where you only benefit from the plate->gear productivity. This would make long crafting chains actually viable with the more stages in the process the more value you get out of the whole thing. It would also give a purpose to the recipe prod item buffs for example (I just bought all nauvis science and belted out a fully stacked belt to my labs at some point. I went from 90 spm to 90 sps, no in between lol).
11. Speaking of the item buffs to recipe prod. There is a lot of cool stuff you can do here with space travel. For example, what if you make the planets linear instead of in any order. Then you can add asteroids that require either uranium ammo, or magmatic to kill and it is only really viable (without shipping up to the platform uranium or tungsten) after a certain prod level. Before that, you have to supplement the ship with uranium or tungsten since the asteroids don't drop enough of those resources to offset the cost of destroying them. But... I suppose I'm starting to ramble. I'll leave it at this.

All in all, I had fun though I think the mod sorta devolves into a strange infinite ore mod for much of its playtime. Dunno. Maybe I played it wrong. Thanks for making it.

Bugs:
1. Near the late game, I noticed I sometimes couldn't use the 'execute one trade' button with no coins in my inventory, but enough coins in my piggy bank. Seemed intermittent or at least I had trouble reproducing it. Taking the coins out of my piggy bank allowed me to trade the items.
2. Clicking buy max on the quantum bazaar with 300,000 extra inventory slots freezes the game indefinitely. It doesn't even crash. Just locks up.
3. After updating to 1.6.8, trades don't work. Train trades function fine. Quantum bazaar works fine. But coins placed in hexes don't enact the trade. It seems to only affect generators and sinks? Other trades work fine. (Edit: its consistent. Some hexes work, others don't)

After some looking, I found that there are some trades that are working in my save. Exiting and reloading doesn't fix it.

Also, upgrading a hex's quality breaks wire connections

Also, upgrading a hex's quality breaks wire connections

Many of your balancing concerns are solved by one mod setting, "Base Trade Efficiency" (BTE). The default value of this setting is a midpoint between what people get hooked on (BTE = 1.0) and where the game is actually balanced (BTE = 0.4 or lower). What BTE does is it reduces the return value from trades. For example, BTE = 1 means trades preserve 1:1 value from input to output, and BTE = 0.4 means it's a 60% loss of value, etc. Naturally, the consequence of this is that BTE = 1 means that the first trade productivity upgrade enables infinite item generation via trading loops. With BTE = 0.4, a trade productivity of at least 150% is needed to produce infinite items (so you don't get there until way later in the game, and even then, the rate at which items are generated for free is significantly reduced).

That said, I'll address your bullet points:

1. The logistic request idea seems good. I can eventually get around to implementing this.

2. The coins in trades are displayed as one lower tier of what normally would make sense. For example, a trade containing 22 gravity coins in a slot would instead be shown as 22x100k hex coins, even though it might simply make more sense to show it as 22 gravity coins. I forget exactly what the threshold was where it goes up to the next tier, but I think it's 1000. So 1000 gravity coins is shown as actually 1000 gravity coins instead of 1000x100k hex coins, but 999 gravity coins is 999x100k hex coins. I should probably just lower that threshold down to 10 so that 9 gravity coins show as hex coins but 10 gravity coins show as gravity coins.

3. The idea I've had from the very beginning of this mod (almost two years ago) is that you play Factorio normally, but trades here and there give you options to make more out of what might be useless to you. For example, you're ready to go to space, but you have this massive stockpile of roboports that you don't know where to put anymore. You can sell that stockpile for tons and tons of coins, even if it's at a 60% loss or whatever, and what you do with the coins is completely up to you. Or maybe you turn them into a handful of asteroid collectors at a nice quality. Depends on your trades, and that RNG can be very fun if you approach it from that perspective. But why isn't this the default gameplay loop of the mod in its current state? It's because somewhere along the development of Gridtorio and Hextorio, the community got very strongly attracted to the cheaty way to play the game (that is, with BTE close to 1 so that infinite items are possible), which makes sense because cheat mods are extremely popular (don't know why, but they are). I try to give what the players want. The more popular way to want to play the game is with infinite loops. Although, I'm convinced that if they were to just try the game with BTE = 0.4 from the very start, they'd know no difference and still enjoy the mod.

4. I've had a Quantum Bazaar feature planned for months, where you can click one button to quick-restock all of your missing personal logistics requests using coins. Just haven't gotten to it yet.

5. This is due to the fact that almost all item buffs have exponential growth curves. I tried to make it be balanced under a certain amount of coin budget for upgrading, where once you have 1 to 10 hexaprism coins for upgrading all item buffs, that brings you to a good set of buffs that aren't so OP that they're unusable but are still quite amazing in comparison to what vanilla ever gives you. My oversight was in the balancing of coin acquisition potential, whether through strongboxes, trading loops, or the simple production-based selling of items. Two solutions exist for this balancing issue, where the former is more robust / resistant to exploits: Change all item buff growth curves from exponential to linear, or further balance coin acquisition potential.

6. Strongboxes are very good when BTE is low, like around 0.5 or 0.4.

7. (This is a repeatedly reported concern.) Using that button on the right to select an item was the originally intended search feature. But I had no idea it wasn't obvious to others that it was the search function.

8. The fastest way to level up from silver to gold stars is to rank up items from all planets to silver stars such that they show up on Gleba or Nauvis so that all items are easy to rank up. Using eggs is the first obvious way to do it, but using the unique bonus of silver-ranked items, it's quite an elegant way to make silver ranks uniquely useful (IMHO).

9. Aquilo's item values are massively unbalanced, not because I wanted them to be but because my solver isn't perfect. I've been trying to make a good item value solver since the beginning of Gridtorio (again, that's almost two years ago). This is not as easy as it sounds. I've made several devlog posts about the advancements in the item value solver, and these improvements have been great, but it still can't handle the sheer complexity of Aquilo's production chains as they depend heavily on interplanetary shipments.

10. With a low enough BTE, exploiting such a fast trading speed can only mean that your factory has been scaled large enough to support it.

11. This mod is fundamentally an extension of vanilla gameplay. Making the planets linearly sequenced (where the player no longer has a choice for which planet to visit first) takes away one of the best features of vanilla Space Age (IMHO). I've balanced quest rewards on these inner planets such that they complement each other in a similar way to what Space Age does. For example, epic quality from Gleba massively helps your other planets, especially where you're quality farming (Vulcanus or Fulgora typically, if not in space). In parallel, Gleba's piggy bank feature from this mod pairs very nicely with Vulcanus' cross-surface teleportation upgrade, finally allowing you to teleport coins easily. Keeping the mod centered around vanilla in this way is important to me.

I really appreciate your thoughtful, thorough, elaborate feedback. You mentioned real issues and provided valuable insights, and the discussion is important for improving the mod all around.

Regarding your recent trading bug, it is fixed in 1.6.9 now.
Regarding the wire disconnection upon quality upgrade, I'd have to look into how to perfectly reconstruct wire connections for the upgraded entities. This happens because there's no way to "upgrade" the quality of an entity without replacing it with a whole new entity altogether, which means the original hex core must be deleted (breaking connections) and immediately replaced. Yes, I did have to make it carry over inventory contents when I implemented it.