paypal takes a cut too, so every transfer you do would result in loss of money.
also, whats to stop person M stealing all the money (moderators aren't that trustworthy you know!)
also, this is why most companies pay you after you've done the work, and a service like this would be a bit rediculous. There's no need, I like to have a decent connection and trustworthy employers.
you can normally tell if someone is going to rip you off. Judging characters and making decision is all part of the business world. I don't think i would want someone to take a cut for doing that for me.
plus i don't really think this type of thing should be anything to do with an art critique board, If you think it would be a good business venture why not set it up on your own website.