It might be tricky to implement, but I'd love for literally useless improvements to be unbuildable in systems. For instance, there's no reason to build Endothermic Structures (extra population on tiny or small planets) in a system without tiny or small planets. It might help out the AI as well.

I strongly support this request. I even would go further and make some improvements hideable (e.g. grey them out).

This suggestion is very similar to /#/endless-space/forum/28-game-design/thread/12258-ui-exclusion-of-specific-system-improvements and the linked suggestions in that thread.

This thread is linked to the former and moved to the archives.