I like the idea of adding post-rocket technologies, but basically turning off productivity and efficiency modules kinda kills the mood - for me PMs are really big deal, as they solve throughput issues in late game without the need to redesign my main bus (which would be a pain) - it's a good mechanic to avoid UPS-devouring megafactories, since noone wants to play at 20 FPS, and discarding it only hurts player. I guess the real reason to turn them off was that you could not enable PMs for your new intermediaries. Bergius Process mod have a nice script to solve that issue. With PMs one could easily launch one rocket per 2-5 minutes, so you could keep them on vanilla 100 parts.

Other than that putting some vanilla technologies behind the Science pack4 wall seems a bit odd, and I'd be happy to at least see an option like "do not change vanila tech" (or recopies to think of it). Also quartz sand-to-glass production just for solar panels is completely unnecessary and seemingly serves no purpose - lithium is a nice rare resource you have to work to obtain in reasonable quantities, but sand is everywhere (like it should be) and only used in a few recepies.

The problem with PMs is that they they work to good with better assembling machines. Same with efficiency modules. It was cheaper to use them than to build solar.
But I want to bring PM modules back. Maybe I will reduce the module slots.

I have only put the power armor 2 and the fusion reactor behind the science pack 4 and I don't plan to add more (Maybe module 3s, but that is another story). Will also add a solar panel mk2 so you don't need the fusion reactor.

You are right with the glass production. With the next update processing units (and advanced processing units) will require silicon wafers from quartz sand.

I'd say bringing "beyond" machines to vanilla number of module slots is the right way to balance modules for them. And as for EMs, the real drawback of them is that they do not save space/UPS like the other two. I hardly use them, as building more solar fields is easy and do not affect UPS as they are extremely optimized.

But I want to bring PM modules back. Maybe I will reduce the module slots.

I'm fine with that, but disabling them entirely is very annoying without forewarning.