Hello
I did a play through of hardcorio that is now done for now. And i like to write what i think about the mod.

My let's play (German):
https://www.youtube.com/playlist?list=PLqL-qMDM6XA9wMsJFZKgdDPt4UqvzNenr

I like the wave based attacks from the enemies. There is more urgency to defend and this i good.

The attacks get stronger and more often over time and it was ok from a balance standpoint. Some times i though i couldn't make it but then managed to survive.

Without the modular armor and a shield i was unable to do anything outside my base. This made everything more urgent -> Will i be able to fight back before my resources run out.

The different weapons:
I never really needed the armor piercing ammunition or the burning ammunition. They are more of a side grade than an upgrade. Most enemy get less damage when using armor piercing ammunition, it feels counter intuitive for me that AP Shots do less to unarmored targets that to armored.
The Roach (armored unit in starcraft) has 100% reduced damage from AP ammunition, that is a little strange.

In direct fight the flamethrower + sniper rifle was enough for most of the work.

Laser and Plasma weapons are a lot weaker compared to the bullet based weaponry. They don't feel like an upgrade considered how late in the tech tree you get them.

The plasma turret is a nice thing, but i wastes its shots on single zerglings, when the main force hits the defense the plasma turret needs to recharge (Maybe up the Charge rate -> more Power drain). So for the tech and costs it's not that big of an upgrade.

Rockets, Mines, Tanks -> All feel way way to weak for the cost needed to use them. tank gets destroyed way to fast.

A better way to destroy the main building in the enemy base. You fight to kill all the buildings, and after you are done the only thing left is the main building. Now starts the boring process of killing this HP strong monster.
My suggestion would be a bomb of some kind, that can only be used when every other building is destroyed. But blows the main building up in one big explosion. Maybe with some charge time -> the bigger the base the longer where you need to defend the bomb.

Explanations:
There are some confusing things in the game that would need an in game explanation.

1. How the regeneration of the enemy bases work (Kill all buildings + extractor first before the main building)

2. The Observer radars -> Better tool tip to hint how the affect the purple bubbles.

3. End Game goal, one can guess that it is to repair the ship to get of the planet but it is never stated. Maybe flesh out the endgame, or put a discription box in when the ship upgraded with all components that tells the player that everything is done for now.

Ellerium:
The mechanic is solid, but the rate for alien science packs is really bad. Maybe up the amount of ellerium that is generated by the extractors. Even in bases that are there for a long time, the ellerium extractors are only around ~200 ellerium ore.

In the end i can only say:
So thanks for this mod, it truly mods Factorio to something similar but more different than most mods do.
I also loved that the bugs and problems i found were fixed in such a short time. I will have an eye on hardcorio and maybe do a new playthrough in the future to see where the mod is going.

I don't know German and Google's auto-captioning and translate is hilarious. Fun video anyhow. :)

I agree with many of your points regarding the weapons. The plasma rifle does so much less damage than the scoped sniper rifle by the time you build it (because of the bonuses accrued by that time) it's basically useless unless you also spend thousands of elerium to upgrade it. It just doesn't feel like an upgrade.

The plasma turret could have a use since it has area damage but like you say, even if you have a whole row of them they all expend their charge immediately on some zerglings and end up adding little total damage output to an array of sniper turrets.

The laser turrets and weapons basically did no damage at all when I set them up. They didn't even tickle the enemies.

I do love the sense of urgency and barely surviving in the beginning, the relentless waves of enemies pounding on your gates and you're in crisis management mode to fix everything up and grow faster and stronger more quickly than your enemies do.

The first few times I played I got some unfavourable maps (very spread out resources) and I lost every time. That's actually great, I like a challenge. I had to get better (and a little luckier with my maps) to survive. I came in knowing just the basics of Factorio (what you learn up until the end of the main game which basically ends at oil refining) and had to learn everything else in the middle of a constant panic (robotics helped a lot more than I expected).