I understand the technical limitation of this. My understanding right now is that the item is removed from your inventory when you put it in a gearset. if it remained in your inventory I can see this being easier to fix. The easiest thing to do i think is to segregate equipable items into a unique tab. much like crystals are currently.

but overall, no. I do not think it is a good idea to require multiple pieces of the same gear, especially since it may not be possible to obtain multiple pieces. (IE, I use Lominsan Officer's overcoat on two jobs, and the bracelet on 3)