I'm still confused as to why people think the Nomads would have anything to do with Earth. The only reason they attacked the Sirians was because they unearthed them, waking them up, and they realised that the interstellar empire they were supposed to be protecting was occupied. Earth has never been occupied by an advanced Alien race - or we would have found artifacts similar to those found in Sirius - so it doesn't fall under the 'care' of the Nomads. They're caretakers, remember? Not an invasion fleet, a defensive one. Even if the Dom Kavosh (or however they like to have their name spelt) wanted to invade Sol, they probably wouldn't use the Nomads to do it. Maybe they have some variant on the Nomads, another specifically bred race, for offensive operations. But I know I wouldn't send an unshielded ship away from the location it was meant to be guarding into enemy territory. You don't have a vast interstellar empire for millions of years by being stupid, y'know.
So I don't think that if the Coalition were to be put in an expansion/sequel, the Nomads would be involved. Possibly some alien that the Coalition themselves had found in their own inevitable expansion would be good. I think its safe to say that the Alliance lost, and judging from their military tactics, assuming the Coalition still existed 800 or 900 years later, they're going to be expansionist, hostile, manipulative and tricky. Perhaps it could start off with an exploring Coalition super-carrier trying to make peace with their age-old nemesis, only to double-cross them? It seems to be their favourite tactic - from the intro movie of Starlancer to the Dark Reign ion cannon they base their tactics on lies and acting. That's only if the Coalition are involved. I'd like to see how they're getting on. I don't want another Nomad storyline, that'd get quite dull. There should still be some 'unknown' jump holes so you can meet up with them though
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Coalition technology would be, say, 50 years ahead of the Sirian houses. Thats giving them 50 years of stagnant development to mop up the remaining Alliance forces and establish their power. As they had those mobile warp hole generators for CARRIERS, and carrier-mounted shield generators, and were dabbling in cloaking technology very early on, I think its fair to say that they may have some advantages in technology terms. Those technologys are pretty advanced compared to the Sirians now, and they are from 900 years ago. They must have some pretty amazing stuff out there. THey already had an industrial base, ravaged by war though it was. The various Sirian houses not only had to spend a few years - a hundred? - traveling to Sirius in the first place, but also had to spend time figuring out ways to survive, then building up some cities, then building up industry, then getting back into space, then colonising some more planets and havesting materials from asteroid and nebula fields, before they could spend any significant time on technology development. I think that saying the Coalition is only 50 years ahead is actually quite generous. If the Coalition, or any enemy from Sol, does get included in any expansion, we could be looking at an amazing leap in tactics.