OP, are you are of existence of OpenBazaar? AFAIK it's most decentralized marketplace i've seen, although i never buy anything from there since it's far from user friendly.
Let's say that there's an issue with package's content and the sender claims he sent everything right, the recipient claims the content is missing/incomplete.
Do you have a good way to find out if it's the sender or recipient lying or any of the "couriers" was skilled enough to steal without leaving traces on the package seals? How will the reimbursement handled?
At least for dispute on centralized marketplace or online shop, having video record when creating the package (sender side) or opening the package (receiver side) is occasionally helpful.