Space-based is the wrong way to go for RTS. Much like quidditch, you can't do a decent battle game in 3D because there are too many ways to go around each other. See homeworld for a fantastic effort that sadly has no tactical depth in multiplayer. Then compare that to supreme commander where a key part is deciding which areas to place static defences at, and which to rely on your mobile units to control.

/currently working, very slowly, on an improved TA-like RTS