That has come up before, and it's a way to do it, my problem with it though is that is seems to arbitrary. Since when this comes into question it is generally a case of causing the Wizard to become an NPC the compel system leads to one of three scenarios.
1) The Wizard has no fate chips and therefor become an NPC because the GM is mean.
2) The Wizard has fate chips and unless he wants to retire the character has to give one up because the GM is a little mean.
3) The GM is not mean which means Wizards without Fate chips enjoy the benefit of being incapable of accidentally killing.
None of those are very satisfying to me.
I find that conclusion shortsighted. If the GM informs the group of his intentions(i.e., to compel for death on every attack made with weapon ratings greater than 3 or something) and enforces this consistently, then more reasonable possibilities are:
1) All players who don't want to accidentally kill the wrong person will keep a fate point in reserve to ensure that they'll never suffer the consequences of accidentally killing their targets while still using full force.
2) The players start using attacks with lower weapon ratings whenever they're up against something they don't want to accidentally kill.
3) They do neither and accept the resulting consequences.
If the player of a wizard character decides to go ahead and use high weapon rating magical attacks on a mortal without having a fate point in reserve, they know what the consequences are and accept them. Alternately, if said player has fate points to spare, they can go ahead and use maximum force without worries, because they plan on narratively enforcing their desired outcome(by using a fate point).
It's that simple.