A few more ideas (wonder if Aaron got tired of reading all these?
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Components or facilities that require or preclude the installation of other components or facilities on the same planet - for example, installing Crew Quarters (instead of a Master Computer) would be a requirement for the Telekinetic Projector (or who would be doing the telekinesis?
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Make ships and classes moddable subclasses of some base "stellar object" class, thus making the handling of ringworlds easier (could be constructed like a ship but populated like a planet) and allowing the much-requested space colonies and ark ships
Ringworlds and Dyson spheres that take up multiple sectors (assuming there still ARE sectors
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Races that have different population masses, and lifesupport technology to reduce the amount of "overhead" space used in transporting population as cargo - early on, population transport could be like in Proportions (100 kT / 1M), but then it could reach P&N levels (20 kT / 1M) with advanced life support systems, and maybe even stock SE4 levels (5 kT / 1M) with some sort of molecular reconstitution technology