Found an artifact in the wowhead DB for an item “Tabard Lost & Found” which, upon opening would reward a currently unobtainable tabard. From what I understand, this item was designed in the original Cataclysm PTR yet, never made it into the game. My idea would be to implement the Lost & Found cache with a possible change, maybe (since it’s been almost 20 years since release) give us a chance to obtain some of the most sought after, unobtainable, TCG Items.
Personally, the way I would like to see it is something similar to the T3 quest chain in retail. Obviously this would probably take more work and money than it’s “worth” but a man can dream right?