Blizzard added the raid sets and PVP sets, but they left out quest sets, dungeon sets, and dropped sets. I would like to see an addon that takes on adding all of these to the Blizzard Appearances set tab, both in the collections window and at the transmog vendor.
Set Collector started doing this and died off, but also uses a different window. I'm asking for something incorporated in to the default setup and available at the transmog vendor.
The lists of sets already exist as addon sets, too, in the Mogit addon with the Wardrobe module.