I don't know about US4 but I know what kind of Space game I would love to have.
I would love to play a game similar to Nation States but more and space.
Like a Space 4X game and Nation States had a baby and was an MMO.
You create a game account and you are given a randomly generated solar system but obviously nothing that makes anyone more powerful than the other but this will allow stuff like resources you can only get by trading with other players or exploring and expanding your empire.
You can join a constellation which is like an area of a galaxy you want to be in. So you can join your friends and have more of an effect or be effected by them more often than people outside your constellation.
Or maybe each 'location' can be a galaxy. So I can join my friends who all play within the "Creamy Way" Galaxy. So as I said before we have more of an effect on each other than we do other Galaxies. Then you can have issues you have to take care of. Planetary Disasters, asteroids, pirates, political issues. Searching and harvesting resources in your system. Creating treaties and trades with others. People can write Galactic Laws and have votes on them.
Not sure how wars would be done though.
Then there can be Universe stuff which effects all Galaxies.
Basically I love 4X space games, NationStates, and role-playing.