Well, it's not less complicated, but I had an idea kicking around my head for a while.
Basically, the higher divisions get more chances for Prize A. Prize B and C would go to any division, so the following only applies to Prize A.
Div1 - Up to 4 Prize As each month
Div2 - Up to 3
Div3 - Up to 2
Div4 - Up to 1
Div5 - None
This is not meant to harm Div5, but that Division is considered to be more of an introductory division, so I've left them out. I've no qualms against letting them choose a prize, though, so you could just bump each number up by one.
Like I said, that list is how many times any one division could win Prize A each month. The winner would continue to be picked simply by who has the highest P100 score that week. The Prizes B and C would go to the division winners with the next highest scores, regardless of division or previous winnings that month.
I guess it makes some things easier and rewards those in higher divisions for their harder competition, but it is another bit of info to keep track of.