Slynky your idea is very similer to what I suggested Last week, so of course I kind of like it.
However, you fell into the same trap that I did when calculating the outcome. Your results are only correct if all four players have the same score going into the game. When I started running some numbers using different Ratings going in I got quite different results. I believe it's even possible, given the proper distribution, for the second place player to collect more points then teh first place player. At least I think I had one that came out like that. I may have messed up though. You formula is kind of complicated.
I'll try to run that again tonight.