This is a decent idea - I've always had the idea of a payment processor that would give low spreads and work on popular online sites like Amazon, eBay, etc.

I believe this could work - purse.io comes to mind for a really popular app and it's the only one out there which allows you to pay for Amazon with your crypto-currencies, works pretty well but the rates are pretty shitty.

Good luck op, this project has a real use.