In that case, that sounds awesome. As a mage, I'd love to be able to *really* experiment with magic.
I imagine my Breton character sitting down in the top loft of a Mage Guild Tower, on a chair in the middle of a mystic, runed circle, book piled high around him.
An Idea strikes him and for the next three in-game days he stays there. Maybe he loses some skill points for Atheltics because hes not moving around.
After three days, he casts the magic spell and according to his "spellmaking" attribute that he would have, there is a chance the spell will work and a chance the spell will backfire, permanently damaging stats until he can find an elder magician to cure him.
That's what I would want from the game; real life-and-death decisions, the possibility of something greater, balanced out by the fear of the unknown and danger.