Future expansions.

Wouldn't it be better like this:
I: 2 uses of magic per turn
II: 3 uses
III: 4 uses of magic per turn
IV: 5 uses of magic per turn
This would improve the balance.

Okay. Fireball + Lightning + Explosion + Time Stop + Teleport. Isn't that a bit too much? I think this option would be optimal:
I: 2 uses of the spellbook per turn, the first spell can only be level 1.
II: 2 uses per turn, the first spell can be level 1 or 2.
III: 2 uses per turn.
IV: 3 uses per turn.
The ability could be gained, for example, when the Academy's troops are idle.

But the faction abilities don't work that way.

Perhaps the developers will introduce variety with new factions.