Good idea, I could definitely see Wizards inscribing various runes or sigils on their armour.
Easiest way to do it is to have various advantages and disadvantages for using armour. For an instance, war mages could fight in full plate, but their magical ability would suffer. Some would eschew armour completely - their magical power would be immense, but they'd really vulnerable to firearms. That'd open up interesting possibilities for the player.
I don't like class weapon restrictions myself, I'd rather see them removed (that said, some weapons would suit specific playstyles more); on the topic of wizards, however, I just think that a rapier would fit them pretty well, being a very elegant weapon.
It'd definitely look unique, I reckon.