This is a completely crazy idea, but what if different parts of the tool/weapon/armor actually DID go bad?
This is not the same system as the OP suggested, but a mutation of it.
Perhaps each time an item had to be repaired, a different material and craft were required to repair the "part going bad". In rare cases this could be an entire part rather than simply the same old material.
"Oh, looks like the hilt on your sword needs to be replaced this time ... "
I admit that this would make it
harder to repair than the current system, but would provide more depth to the current repair system, and a little bit more interest for crafters, albeit at the expense of those using the items.
Perhaps as a compromise, using non-preferred materials (allowing for more crafter types) counts as a "patch-job", taking the repair to 90% or 95% instead of 100%?
Just some random thoughts ~~ please don't take them too seriously
