I like the Monk idea. He would be trained in the Holy and Mind school. He'd have a counterattack against melee attacks Also he'd have monk only cards like "Mana over load" (full spell) your monk loses his quick cast and Action next turn.   Gain +10 mana.  

and meditation chamber.  Zone exclusive conjuration.  During the channeling phase your monk gains +x channeling for every non-mage friendy creature in this zone.      

 Just some ideas off the top of my head.