I almost did a complete playthrough (was not able to finish because of biters; see other thread) and overall I enjoyed the experience. The premise is really interesting; it could become a great mod with some polishing that would make it less feel like a (nice) prototype.

First obvious step seems to me to remove useless features from the tech tree:
- Trains are useless
- Most things military are useless (except armors with inventory size bonus and/or an equipment grid)
- Mining productivity is useless

I understand that it is easy to disable these if we are only considering vanilla techs and that it might require a lot more work if the techs are coming from other mods. Eventually, it would be nice to support the big mod suites (ex: Krastorio, A&B, Py, ...) Maybe you can start by supporting vanilla techs and give a warning in the mod description about techs from other mods.

Also, I found it quite (too) easy to have several Factorissimo techs unlocked from the start (ex: infinite recursion). I find it nice having to deal with a the limited space provided by my factory at the beginning; having infinite recursion right from the start feels overpowered.
I guess it would be nice to find a way to discourage abusive recursion, like by giving an increasing penalty for every recursion (ex: -10% machine speed per recursion level; it could be implemented like if a beacon with a negative effect was covering the whole factories).

Concerning the techs introduced by this mod:
- Extra resource belts seem way too easy to acquire to me. I always had way more than I needed. Maybe those techs could be further down the tech tree and cost a lot more science to research.
- Some of the extra resource techs seem quite overkill. 7 blue belts of uranium ore...? Who would need that...?
- Extra factory belt speed 1 & 2 are overpowered (way too easy to acquire). It makes it too easy to double/triple the inputs. Maybe you could add techs in between, like going from a 100% full yellow belt to 60% full red belt (instead of 100% full red belt), then 70% full red belt, etc. And keep the full blue belt for late in the endgame

I also found some little quirks about how factories work (ex: having to manage electricity throughput and fluids update rate, among others). But I guess they are more related to the Factorissimo mod than yours so I won't bother you with these.

Overall, I think this mod has a lot of potential (good job for putting it all together!) and I hope you will continue to work on it :-)

Thank you for the feedback!
There is a few things that I don't want to do, because it can cause issues:
- Removing research. Mods can put research as a base to one of the removed researches, which can remove any researches that are based off of it. For example, a better mode of transportation could be based off of trains (such as monorail or hovercraft). If I remove the train research, I remove the research of the hovercraft or monorail.
- I understand the too much research already done from the start. What would you think about the research still being there, but a bit cheaper than default? You can't go to many places without recursion, and it costs 2000 automation + logistic to research Tier 1, 5000 automation + logistic + chem to research Tier 2. IMO it could be more like 500 and 1000
- The -10% machine speed would be interesting. Not sure how beacons affect recursed factories, but I'll try to do it :P
- Resource belts are understandable. I guess that they could have more dependencies, such as 3 more belts would need trains. 5 more would need Braking Speed, etc.
- Tiered belts could be much harder to obtain. Red belts would require chem science, blues would require fusion tech. After that, belts would just be based on each other, such as other mods (like Factorio Extended+) adding in extra tiers of belts. They would be behind the blue belts, so it would be very hard to unlock them. The research cost would rise exponentially ($$level^2$$ sounds like it could be a nice number)
- Ores are automatically generated, so even other mods that add in ores can still work properly
- The other belt tiers sound very nice. Default speed of 50%, then you can upgrade by 25% improvements

What do you mean by electricity throughput and fluid update rates, or even other stuff? I can't edit Factorissimo itself (since this is not Minecraft), but I can try doing something, such as fluid "teleportation pipes".

Thank you for your feedback! I find it fun to change Factorio itself. In advance, I won't be incorporating these changes very soon. I have other projects that require more attention as they will break quickly if I don't give it to them. I hope that I get to work on this in the next month, or at least the summer holidays.

Thanks for taking time to respond and even consider some of my ideas :)

Please note that I never tried Factorissimo before; I found your mod to be a nice opportunity to get familiar with it. The kind of things that were not obvious to me at first were of the kind of fixing the electricity output (for my factories producing electricity), getting proper fluid throughput by putting fluid update rate to 1 tick everywhere (... is that the right thing to do..? not clear) and also not being entirely sure at first how the belts input/output "magically" work. I guess some improvements can be made but I am aware that, as you said, it is not part of your mod and you can't edit it.

Because I never tried Factorissimo before, I didn't know that tier 1-2 research cost is 2000-5000. I agree with you that it would make sense to make it cheaper since those will be quickly needed :)

Considering the removal of useless research, I understand your point; maybe you could provide it as a mod option. Or maybe several options, like "Include military technologies", "Include train technologies", "Include mining productivity technologies". As to what should be the default for these options, I personally think that they should be disabled by default but I understand that opinions might differ from mine.

Now that I think about it, an alternative to resource belts could be having new kind of factories (like the T1, T2 and T3 ones) for each kind of ore. For example, you build and "Iron ore factory", you place it and when you enter it you find an iron ore patch on the ground that you can mine. That would make the game quite different. That's just an idea that is coming to my mind; I'm not even really sure it's a good however (so I'm not really suggesting it ;) )

Keep up the good work!

The options sound like a good idea. The mine sounds very interesting, too! Would be useful if you wanted a late-game base and a lot of resources, you could just have a lot of mines instead of relying on belts. Could reduce the amounts of belts you would have.

The input and output pipes can really help with throughput for fluids without having to change the tick rate.

If you mean those from Factorissimo itself, then I believe that has been resolved in 1.0.3.
Otherwise, are you talking about custom pipes or something?

I'm talking about those pipes. :-) I'm not saying there's anything wrong with your mod here. I'm pushing back against the idea that the default tick update rate for fluids should be more frequent.

Oh, okay. That's understandable then