This is easy to do - a payment proxy company will spring up that will accept buyer's bitcoin payment and remit a different bitcoin to the seller, minus their co

This is easy to do - a payment proxy company will spring up that will accept buyer's bitcoin payment and remit a different bitcoin to the seller, minus their commission. That payment company will pool the risks, develop profiles for users they trust more, develop technical and other expertise to predict and prevent fraud etc. The seller will then work only with reputable payment proxies to instant payments, or directly with buyers who don't mind waiting.