I always played mage classes in games so maybe I can help a bit.

Black Mage: Maybe instead of summoning zombie or undead we can summon spirits instead? This makes more sense for lower levels, the power and damage of the spirits depends on player's level. If you want to keep the undead maybe you can move it into the necromancy skill for higher level. At even more higher level you can summon dead monsters but only small - medium ones. (I'm uberly interested in this so I put more thoughts to it ^^" )

Battle Mage: Let's just leave the hammers and sword for melee characters. Give the Battle Mage daggers instead.

Sorcerer: What they will transform into depends on the levels. For example, they can turn part of their body at lower level but can turn into a full animal at higher levels.

Talking about levels.. How does the leveling work? Did the level system got hacked too?