You know, way back in college, I used to play Battletech with my roommate. The old pen and paper version. He used to have his own critical hit and critical failure tables, all delineated on a d100 with unique and awesome things that could happen on both sides of the coin. Roll a fail and with glee in his eye he would reach for that sheet and roll out the miserable thing that would happen to you. Roll a success and reap the awesome rewards.
Anyway, this got me to thinking about Bright Wizards in Warhammer Online, and the combustion mechanic. Pushing combustion higher and higher could earn you more criticals but eventually you could blow yourself up.
Why do we not have more of that dynamic in WoW? Specifically in the caster class and specifically with the class that deals with the most uncontrolled magics: the Mage. What do you guys think? Could the system bear a rewards/penalty type system, or is it too much "goblin engineering" and wouldn't be fun?