I think just a payout cut. B pool can keep playing their 3rd and 4th rounds since they paid to be there. But if you are in B pool after the 2nd round, you're payout ineligible. That way there isn't a risk of some fluke situation due to multiple course usage causing a drastic change in the field.
That's kind of harsh; where do you draw the line between payout eligible and non payout eligible? A hard and fast line at the payout cut? Everyone within 3 strokes? Within 5 strokes?