Hmmmmm, now that is good thinking.
I have the ability to machine just about anything. What do you think about me making a alternator pulley with a big "shoulder" on the ouside edge to in effect keep the belt on the car?
While a guided shoulder is always good, I believe the problem is the one way clutch. Since the clutch is designed for the belt to move one way, when the belt starts to slip it is actually going backwards and it 'jerks' the belt and the tensioner causing failure.
Acquireing a new alt pulley should work. The Saleen blower doesn't have this problem because the alternator is turned around, it gets a new pulley in the kit.