Instead of the system being gear related why not make it class/job related? Im thinking about FFIXs system of gems and slotting different unique traits depending on the situation. This would alleviate the keeping of old gear which Yoshi is terrified of and it would mean everyone could benefit from this since people who don't clear high end raids wouldn't need the gear that had said special traits/stats. The system could work the same but maybe using something like clear materia mixed with something else which then would fuse to the trait/stat and they can be switched at will except in combat.