Will this space station be stationary, or will it be like a ship? If it does move, "away" missions to planets or other stations, or even derelict ships would be useful diversions and something to break up any potential monotony. Perhaps "ancient technologies" could be found, researched, and made into special facilities or weapons.
Maybe there could be travelling stores or trading posts.
I think working toward something might be cool, perhaps missions to certain planets, with difficulties based on different obstacles you might face on the way. This would also make an "endless mode" an option for those wishing for that experience as well.
