Making lures into a system similar to gig heads is a wonderful idea. Another idea would be to create some kind of general-purpose lure to cut down on the clutter. Say, for example, a Lv70 GSM crafting recipe that can create a Lv70 FSH lure capable of catching any fish from ARR and Heavensward. And when 5.0 comes out, they could make a Lv80 one capable of catching all Stormblood/Heavensward/ARR fish, ensuring that you'd only need to hang onto the tackle from the current expansion.