Do you think it is possible to add space ships to the game? As far as programming goes, it seems like they could just be treated like any other object.
The differences I could see would be acceleration, deceleration, and course plotting whether it be manual or automatic. Maybe even a form of "hit points" for the ship before it completely explodes and maybe different types of fuel/engines?
Space stations would also be interesting, with size all the way up to artificial planets.