Building on a suggestion from MMA-Analyst's Leland Roling, Fight Opinion's Zach Arnold has a piece on MMA Memories that outlines a pretty interesting proposal for ensuring that fighters will do their damnedest to make weight:
1) If you fail to make weight for one fight, you lose a third of your fight purse and get suspended for three months by the athletic commission.
2) If you fail to make weight for a second fight, you lose half of your fight purse and get suspended for six months by the athletic commission.
3) If you fail to make weight for a third fight, you lose your entire fight purse and get suspended for a full year by the athletic commission.
I think this is a really solid suggestion. The only thing I would add is something to clarify that the three failures to make weight must occur with in a two year time frame or something to incur the increased punishments.