One of my rules for this project is "no new figures". I am only making use of figures I already own, and preferably those already painted.
One such possible army (although it would be small) would be a phalanx of Wagon People of the Karzstan mountains. These are wandering communities, in and around the Fribourg Canton of Rumpwhistle, and he travel in town sized populations with many wagons and horses. The fighting style is not unlike South African Boers, fighting from behind a wagon laager. I have about 8-10 units of infantry intended for this role, only needing rebasing. I also have half a dozen wagons that could serve this "phalanx" (the name they use for an armed camp fighting together. They were first mentioned here: http://chuckgame.blogspot.com/2013/03/19th-century-imaginations-rumpwhistle-2.html
Beyond that, all other possible painted figures that would be suitable are individually based for The Sword and the Flame. I don't want to rebase them. However...
If I stick to my rule of no new figures, but relax the rule on painting, then I could conceivably come up with not only several foreign units (Vulgarians, Trans-Turkylvanians), but also a sizable force of Urbs. In fact, I am planning on it. Details to follow...however, so that I can use them for other gaming projects, I may make changes to the standard Baalkanian basing scheme ( which is currently 12 figures on 4 bases for standard Infantry units).
Finally, another modeling project related to 19th Century Balkania will be some terrain modeling. Again, details to follow.