OP wants a marketplace where the seller will be paid immediately, but that can't work. The buyer must confirm that the product or service they purchased is legitimate. That's going to take time, especially for physical goods that need to be shipped across towns and countries. Smart-contract enabled confirmation that the goods are legitimate aren't a problem. That can be built in. The waiting time needed to receive, test, and confirm everything is in perfect working order won't be reduced with automated escrow.