Congrats, you have made perhaps the best Civ V MOD I've played!

I would add a suggestion that I think can add some D&D flavor to Hero leveling:

You could replace existing promotions for another ones based on D&D 3.5 feats such as:

Power attack: +10% combat strenght
Cleave: Damages up to two adjacent enemy units
Point black shot: +15% ranged attacks to adjacent units
Manyshot: additional ranged attack per turn
Enlarge spell: Wizards have +1 range for ranged attacks
Quicken spell: two attacks per turn, or don't have to "prepare spells"?
Empower spell: wizards have +15% ranged attacks

That was all, thanks for your awesome work ;)