Nice idea.

But the whole idea of OpenBazaar is that it's decentralized. I guess you'll be the "center" in this case. If OpenBazaar becomes big enough, I think this will work (and face competition from hundreds of clones) but if it stays the niche it is today, I'd assume this won't work because currently the only people who use it are people who care about the "decentralized" part. The reason for that is everything else at OpenBazaar currently sucks. (Early stage problems)

I could be wildly wrong though, I'm not an expert in this domain.