It's a good idea, but has to be rethought. As how I see the idea now, there are alot of issues with this system.
If a graphical designer sells a signature for example, the buyers name won't be on the signature, since it's premade. We can't verify things like membership pins. If someone makes a sell, with a false pin, then the buyer will get scammed, and OSBot will be responsible for it. Scripters can already sell their scripts on the store. There's no need for them to have a own store. We can't allow RSGP sells on it, even if an admin gets the gold before the actual sell goes online. With Paypal chargebacks, it will be a risk for us.
Overall, I only see this work with membership pins, but we can't verify these, so that's a really big risk.
I do like the idea of OSBot being a middleman though, it will be a major improvement for our market, with less scamming.
Let the suggestions roll