I don't think there is one, the only solution to fraud detection issue is to build something that will ultimately just become like PayPal is with all it's frust

I don't think there is one, the only solution to fraud detection issue is to build something that will ultimately just become like PayPal is with all it's frustrations and shortfalls. You are also up against regulatory issues (you skirt around becoming a bank = highly regulated) and the massive network effects PayPal/eBay have. I heard that Square had to pause growth to deal with fraud, and they have the benefit of having Visa/MasterCard/Amex as intermediaries.