During the E3 2017 Letter to the Producer Live, Yoshi-P implied making a glamour catalog would be hard...

Of course I have no knowledge of the internal representation of object in FFXIV, but I would like to offer the following suggestions to SE's software engineering team:

Use a representation such as a bit array (01010101111100000), if the at the object id index the bit is 1 then the character has the item available for glamour, if the bit is set to 0 then the character doesn't have the item. If you had a million piece of gear that array would be ~123 KByte big without compression. This bit array should be pretty easy to compress to store and transfer. Various optimizations are possible on the array (range exlusions for items that are not glamourable etc.) Lookup in the array is O(1), so it's fast.

You also don't need to send that glamour gear bit array each time the player change zones, you only need to update it when the player login and when they get new gear. To verify if the array changed, a simple checksum can be exchanged rather than the full array. A more complete lookup can be done when the player try to apply a glamour (e.g. to recover the dye color of the item the user want to glamour.)

The same concept can be used for armoire since it doesn't store materias, nor dyes, nor item status (spritbonding/condition).