IMO, That's a good idea. It will probably harder for Mayweather to accept those terms because of his huge ego!
60/40 with the higher percentage going to the winner is how fights SHOULD get made. It only makes sense that the winner should get a little more. Obviously it would suck even worse when robberies occur, however.
The current system makes perfect sense.... as long as you remember that fighters are paid 1 fight in arears. If you take a title shot for peanuts and win you will get paid for that win in your next fight.