I'd like a vast role playing game with elements of space simulation +shooter +a bit of strategy (direct troops and whatnot). Single player by the way.
So essentially a bit like x3 reunion/mass effect/crysis/kotor/homeworld/total war.
You have the ability to pilot different ships in space, and can organise fleets. In some situations you can zoom out of your point of view, and the game behaves as a space rts. Full size planetoids/ stars... which you are able to fully interact with. So you can land anywhere on a landable body, at which point you are able to get out and go on foot. Then it is free roaming, similar to oblivion (but with a better role playing aspect). The game is also a good shooter (you have the ability to switch between 1st and 3rd person).
In some circumstances, you can zoom out of your point of view and lead armies, similar to battles in the total war series.
Understandably, this would all be a technical miracle. And yes, you'd need some means in order to traverse the vastness of space quickly (giant stargates?). Maybe limit it to a small region of our galaxy).
For multiplayer, maybe the rts bits would have to be removed (I can see how it could work, but would be very complex).
Anything that can come close to this ideal may interest me greatly.