Someone mentioned it would be like a reverse auction house. Why not make it a feature of the new auction house system. You put the items in a "looking to be crafted" section and then the player crafts it from the window.

Also, someone mentioned that the player could steal the items. I'm assuming they haven't done any leves for crafting in the current system. The player doesn't actually have the items given to them in their inventory. They are automatically put into the crafting window when the leve is selected.