I've actually seen something like this once from an FC ages ago in the form of a crafter's bazaar. It was sorta like a garage sale every week, where you could go up to a crafter and they'd tell you what items they'd have in stock and sell it at some discounted price from the MB standard. You could also give them requests for crafts, and you could either pay for their mats or provide your own. They also held auctions for bigger and rarer stuff, with all the proceeds going toward funding crafting leveling kits for new players.

Now for the original idea, if it were to be a thing in the game, it'd have to be 100% player-driven much like that FC crafter's bazaar. Sure, there could be a couple of things that could be done on the development end to assist in this endeavor, but all of this would have to be up to the players.