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

The thing is, the gods send their children to serve and help their followers, while the angels renounced Elrath, because they wanted to rule. Besides, dragons are creatures, albeit intelligent ones, but they could hardly command armies.

Therefore, I still suggest making angels something like a deity for necromancers, but not using them as heroes/units. Instead, dark riders would be a better fit, replacing the Void Spirits on the 6th level. A rider on a dragon is an excellent unit for the 7th level! There are already not enough dragons in the game.