RTF is a global modification that replaces all towns in the game.

How can red and white troops of the Empire be under the command of one player? Besides, "NOT-good guys" are not primarily villains, but mercenaries – you pay them, and they work for you; the point is that they don't care who pays and what orders they receive.

Added 4 minutes ago

What does it mean they don't fit? Any character can play their role, and as they say, "heroes are not born..."
I don't see anything that strictly ties them to a specific city.
In general, I'm in favor of using lore characters (by the way, something might be useful for NHF as well).

Can you give more details – what are you working on? What changes are you making? As far as I understand, the most suitable donors will be crystal dragons; you don't need to change the number of legs, the shape of the wings, or the head. It is necessary to attach an effect like the one on Ylath's artwork, remove the ridges along the spine (you can simply make the texture transparent there).
P.S.: For reference, I will attach Ylath's artwork.