Yeah, this would require a lot of work, but I think it being implemented would take Sythe to a new level.
Having bonded services and sales means that people are basically insured against scamming and such up to a specific amount. For instance, you pay $50 to Sythe, you have $50 on your insurance. If anything goes wrong, your 'insurance' pays for the damages. Sythe would have to charge a small fee for this service, as it being free would not be the best idea.
It would increase the necessity for middlemen, putting a stipulation on the funds such as "Using an official middleman is required for you to be eligible for a claim in the event of a scam". Thereby requiring all users who trade with bonded sellers as well as the bonded sellers themselves to use middlemen. Also, this would increase the necessity for middlemen and would put them back on the fast track as they were several years ago.
I seriously think Sythe should consider this, but it will require a lot of work.