In any game, it is possible to manipulate the rules in order to give you better abilities. In the Dresden Files, this can be done through rebate manipulation- and, at least in my opinion, isn't always a bad thing.
As a GM, if I know the way someone plays in general, and know they can responsibly handle a character that would, in some people's hands, be gamebreaking- I would be all right with that.
They would, of course, have to abide by a few rules, such as structuring the character so they could not steal the spotlight from other players, and making sure they aren't going to go berserk on anything that would be detrimental to the game.
What about you guys?