Yeah, there isn't much ship-wise to go on, but its great show with a rich universe, and I think it'd make a rich mod.
For instance, the Red Coats are meant to be cash-poor, so there ships could be mostly variations on the inexpensive Firefly design, and fans likely wouldn't mind, as long as they are buffed with abilities. In fact, I think its realistic that they wouldn't have any capital ships at all.
The Red Coats are innovators, though, so their frigates would be capable of destroying cap ships when in groups. We could also give them 1 or 2 ships that specialize in sabotaging cap ships and titans in small groups of 3 or 4.
I envision their Titan as being basically an asteroid sporting phase engines, an Alliance planetary shield, legions of strike craft and long range missiles. It could stand titan-to-titan, so would be more than capable of taking "central worlds."It would also serve as a mobile frigate factory, so could go deep into enemy territory and cause real trouble.
The Red Coats would also be immune to pirate raids, and would start the game as their allies, with an ability similar to what the TEC Rebels can research.
And imagine the Reavers as a playable race. I know the easy way out would be to make them the pirates, but what fun is that?
The Alliances' Titan would be that city ship we see in the show a few times...as for their other ships..I'm sure we can come up with ship classes that would seem to fit. \
Here's the playable factions, as I see it:
1. Brown Coat (Loyalists)
2. Brown Coat Collaborators (Rebels)
3. Alliance (Loyalist)
4. Alliance Rebels
5. Reaver (Loyalists)
6. Reaver Dissidents