Bazinga, I think its a great idea, it would work just like anything else that is bought with plat and the traded for gold, as for how much it would be well that also would be exactly like everything else, it would find its level based on supply and demand, in economics this is refered to price discovery. It works perfectly well everyday on the stock exchange. Ok that may not be the best example, dang those rogue Wall st traders.
A better example in the real world would be your local Trade and exchange magazine/website.