I dont know though I'm not sure that the current series would allow enough civilizations. I mean you would get the Solamnics, Dark Knights, Minotaurs and maybe a few others but I as thinking more along the lines of a generic Dragonlance world. And with the time period I'm thinking of medevial style base units would be better than Roman style.

Solamnia- In the north(Solamnia). Heavy Cavalry probably the best in the game. Decent selection of Infantry. Probably the largest starting faction. Unclear whether or not the solamnics would have there gunpowder bombards yet.

Qualinesti Elves- In the southwest(Qualinesti). Archer units and units specialized in hiding. Poor selection of cavalry, average infantry. Starts with just the Qualinesti Forests.

Silvanesti Elves- In the southeast. Units same as Qualinesti's. Starts with Silvanesti forests.

Minotaur Nations- On the islands north east of the Mainland. Best naval units in the game. Very heavy infantry (Berserk), poor cavalry and archers. Starts with all of the islands in the Northeast.

Ergoth- On the islands to the west excluding Sancrist and the southmost half of Southren Ergoth. Naval units close to minotaurs. Very Similar structure to Solamnia except with less heavy cavalry and more heavy infantry. Kind of an older Solamnia.

Dark Knights- In areas such as Neraka and Sanction or farther North. Almost identical to the Solamnics.

Ogres - In the lands of Khur in the west between Sanction and Silvanesti. Very Heavy infantry. Would have "May charge without orders", and berserk.
Little or no archers or siege equipment.

I'll post more later as I think of them.