Whoa, hold off! The whole reason you guys can't agree on the scale of the project is that you're subconsciously factoring in the gameplay design costs, and that part could be worked on here and now. Of course, the questions must be present before the answers (and don't give me any H2G2 crap -- Douglas Adams, unfortunately, can no longer defy that law) so I'll just discreetly take command of the "question" side and start asking some stuff.
First of all, there's the question of 2D vs. 3D. 2D requires that the images be rendered beforehand; this costs a lot of money and hard drive space. If you used an OpenGL-based 3D engine, however, you could trade off those costs for others (development time and audience -- you'd need a higher-performing machine to play it). Composited special effects would be tougher in 2D, by the way -- I assume you're all familiar with the size and design limitations imposed on EV ships? Those'd all be gone with 3D.
Next, how would you structure the objectives in the game? It would be pointless to have a pre-written storyline. I would suggest giving players the ability to establish their own organizations, permitting them to be "upgraded" once certain benchmarks were reached (ie. population, systems controlled, # of servers owned, etc.).
............. Eh, I've run out of questions to ask and suggestions to make. Someone grab the torch.