I feel that always the best way to understand something new is to have a UCS.
Its a simple one, just to examplify if it is possible or not!
Lets say we have 3 agents: buyer, service provider, merchant.
Buyer makes a purchase via service provider (lets say ecommerce site). It creates and address with amount to be transferred. This amount is transferred from buyer's account to a Clearing account (Smart contract). After a period when service provider confirms that goods are delivered (or just does not issue a stop address), the Clearing account sends (self executes) a percentage of the deal to merchant account and a percentage to service provider as a fee.
10x for any thoughts. I bet it is a bit more complicated.