Firefly's wouldn't be too bad. A nice medium transport really. (That model is horrendously out of scale) A firefly is roughly the size of a Behemoth freighter, and we really don't have allot in the 1000 - 2500 cargo transports.
A Firefly class would be a good fit as a medium sized transport that can hold its own, say, traveling from House systems to border worlds/lands. There really isn't a common transport for the factions that live off on the edge. In terms of the "story" to the Firefly Class ships, it was an old design compared to its contemporaries that was once a widely used workhorse to carry goods and people over medium to long range distances, ideal for work in the "Borderlands" of the " 'Verse." It is also widely used for smuggling. I can really picture doing contraband runs in this ship.
Cargo range around 500. Probably would not want optimal weapon class above 8, but that is really hard to figure out from this point.
Of course, I am biased because I am a fan (Browncoat) at heart, and in terms of game play, it would be a good fit. And it would please many of us.:yahoo:
if we allow this ship in the mod then we are going to have every single guy who thinks that a BSG ship or a Star trek ship or a Star wars ship or whatever show is FL-ish posting threads about "ZOMG!111 i want that zhip!!!11"