I've thought about this myself actually, but if it were an out-of-game system(as it would have to be, due to the source code missing) then players could lie and say they rolled a higher number than they actaually did. Or perhaps if they didn't lie, but the scenario was a kitten attacking a wolf. Mhmh, I like th concept, but I'm not sure how well it's work out.
(This should be in game ideas, perpags some mod-floof will move it ;) )