I'm thinking along the lines of Asteroids, Comets, Meteors, Dust clouds, Random floating things in space (e.g. Proceedurally generated space junk) and Dark matter globs. Anyone know if they are going to be in the game? And whether or not these can interact with planets like huge meteor impact that a city might want to preemptively stop?
Personally I like that kind of thing, but whether or not its in the scope of this game is another question