Wow, I can't count the number of times I've daydreamed about a realistic space combat simulator (Orbiter-based or otherwise) on the walk to my old day job... Best of luck with this. I'd love to be a beta tester, but I unfortunately don't have the time right now. I'll keep checking in, though, for sure.
I'm a little uneasy about sullying our peaceful Orbiter with associations of war, but we've known since before Aristotle that all stories require conflict, and what conflict is more immediately compelling and interesting than the armed kind?
Edit:
I drew this a while ago for a similar topic, but y'all might get a kick or some ideas out of it.
Only armored on the front side and the tops of the radiators, big tube of propellant in the center, whole thing a little bigger than a space shuttle... Probably a little more stylin' than a real combat spaceship would be, but since it's a simulator, visual and auditory cues have to make up for the lack of real danger. We'll say it's bulked up to withstand the stress of evasive jinking.
The idea would be that a large crewed carrier would take these guys to the battle zone, whereupon it would launch them, then hang back and act as a kind of AWACS, picking out targets from civilian traffic and debris. These half-dozen or so AI-controlled gunships would then close with and engage the enemy, and be recovered or not depending on their trajectories. They've got all three "traditional" space weapons (laser, railgun, nuke) for you to try out.