Need a Bigger Bag achievement

Items that are given as a quest reward like Puntable Marmot or archaeology item would be real easy to determine if you have them. Likewise for anything on the Going to Need a Bigger Bag achievement.
But another thing that would help with storage space I think would be to have a vendor somewhere in every zone that sells every possible quest reward that you could get for 10x the vendor price,euwowgold.com but only if you have the quest completed or Loremaster of <Zone> finished. That way you wouldn't worry about vendoring items with unique looks that you may later want for a transmog. I'm saying 10x the vendor price so you don't use that to abuse diesnchanting because it would be inefficient to have every item undisenchantable.