If it ever were implemented it'd likely just use whatever the Armoire already does. Just a series of bit flags that's not written to as frequently as anything else. Just have the client read from it on request so it's not having to maintain/cache that data on the client somewhere.

A single kilobyte of data can hold 8,192 pieces of on/off switches for gear acquisition. Pretty sure that's enough to cover everything in the game as it stands.

If they want, they could just make glamor prisms be used to registering a piece of gear in a catalog so those don't become obsolete, rather than having it be an automated process like other MMOs.