Ebay, Alibaba and other platforms take their fees for the services they provide: the users can open the dispute, they can get their money back if the seller deceives them.
Will you be able to offer such services for the users? Will the users have any guarantee that they can close a deal with minimum risk?
I think it will not be a problem. None of the sellers will want to spoil his reputation with bad reviews and controversial things. Directly to preserve the reputation, of the sellers go to meet buyers in disputes. It also happens in Ebay or Alibaba.
However, I am more interested in what about fundraising for the project. What is the information.
They offer the so called "distributed escrow" service on the OmniBazaar marketplace, but as I remember this would be only available as a paid option.