Some suggestions. (I love this mod and want MOOR!, especially more of the buildings).
Now that we have pets I am wondering, we can have a memorial for dead crew, how about adding in a Pet Cemetery? (Because you can).
How about planet based artillery? It shoots at fleets from the planet? That would make planets as a goal to quickly conquer, could make it a very rare encounter, maybe not craft-able but if on a planet it can be captured if you take it over.
How about a Tesla based shield grid, it sends out shocks from the planets to fleets come to close? It sounds interesting as a planet based defense that acts the same as the artillery but at very close range instead. Could maybe have the effect that as you enter into battle with the space station your fleet start off with an EMP damage that needs cooling off at the start of battle? (Could be cheesed by sending off one ship to stat the battle and then send in reinforcements).
How about fantasy/sci-fi buildings, like floating islands (anti-grav or engine based?), underground complexes or cave systems/dungeons? Ideas could be take from Stellaris like prison planets and alien ruins worth studying as well as other things I can't recall right now?
How about like Stellaris and an adaption/modification of Starsectors debris fields and ruined ships. You could create a story based encounters with random dice rolls as to the outcomes of encounters. Basically find a scraped/ruined ship that crew board to explore, working like stellaris instead of how it does in Starsector with mini stories and cool finds, like you gain a history log from the ship to sell to factions that acts the same as a scanned planets data.
How about Mega Structures like those found in Stellaris and the mega mod Gigastructural Engineering & More?
https://steamcommunity.com/sharedfiles/filedetails/?id=1121692237https://docs.google.com/document/d/1HXW5F6S6UWESkPSh6OaxWvHwZyYAGYSuCBnCAn1B5g4/edit#heading=h.76tyu3aoyd09Or massive ships that act as a planets? Not sure how it would work but sounds epic to land fleets onto a space ship rather than a station.