Skull of Shadows (SoS) is a Polish mod that replaces all the factions.

Balance and NHC (New Heroes Content) are incompatible in the same sentence.

Balancing so many units could take more than a year. And considering the addition of a ton of new creatures with a million abilities each, it would be problematic, to say the least. As far as I'm concerned, it took so much time to balance the original version with a minimum number of creatures. I agree that clunky models (and there are many) are more of a deterrent.