This is great. I'm not a IT developer but a financial analyst, but I just know this idea is what bitcoin need to ease the difficulty for the merchants to adopt bitcoin as a mean of exchange value.

I have a small tip for you, if you don't mind. You can talk to mtgox, campbx and other exchanges, and ask for a premium commission rate for you.

P.S
If I were a merchant and sold something with a 20% gross margin, I would like you to convert 80% of the BTC I got into USD and keep 20% of them as bitcoin. So why not offer the choice to your client? If only black or white choice, as a merchant, they will get running-out-of-working-capital problem if keep all the money in the bitcoin they get paid.

 If you offer the partially-exchange offer to the merchants, it will easily get them to keep some of them. later, They will spend more time to know about bitcoin and may try to use bitcoin themselves. This will make it a more widely accepted currency.