Again, all of these suggestions would be much better than the current beta system, but as Gyson implied, the only difference between level 1 and level 5 Repair under this Stabbey system would be the former would need to buy X more hammers than the latter in order to maintain all equipment in mint condition. That is a noticeable difference (albeit depending heavily on the availability of both gold and repair hammers in the final game build), but it just doesn't seem to give much of an incentive (or gameplay interest) to increasing the ability beyond level 1.
That's why I would again suggest (either instead of, or in addition to, Stabbey's suggestion) something like higher levels of Repair allowing you to repair higher value/more "complicated" (e.g. magic/legendary/etc.) equipment, and even slightly improve the equipment (in a way that wouldn't obviate the need/incentive for Crafting) at the highest level(s). I'm intentionally avoiding charts/stats here; I just want to throw the general concept out there.
