Here's a unique twist on the avians that I'd just like to throw out. Haven't really thought the implications through in detail but thats what you guys are really good at.
Think of them as a human-like race that has mastery over supernatural avian-beasts.
No stables, they don't use horses
Special building added: Nesting Grounds can store: up to 25 Griffins (or whatever is balanced)
Unique Spell: Avian Empathy
off spec 2/0
def spec 0/5
elite 2/5 ?value? ?cost?
Griffin (Horse-analog) adds 4 offense to any offensive unit, which could be soldier, off spec, or elite.
Griffins are generated via race-unique spell "Avian Empathy", a random number of Griffins are added to the Province Reserves. Spell difficulty: Moderate, Rune consumption moderate.
Griffins decay with time and suffer combat losses, so mystic activity and rune supplies are required to maintain an offensive army.
What do you think? Its unique that's for sure.