I know you want to make this a great game but I think you ran into the same problem as Rising Empires did: Everything starts great but, it quickly starts to fall.
Therefore, in order to ensure the survivaility of such a type of game, I have a proposition.
What if instead of making the focus of the game on 'faraway empires', we do not make it much like the agreed concept of SPC:Sci-Fi? I mean, we start with three or more great Earth nations viying for influence and power in the colonies. While some players will take the role of the great powers, most will be colonies, and this will enable a good gameplay mechanic, which has been succesful so far. This will also enable the Avatar team to have more control over the different planetary cultures and economies.