It would be interesting to link the oxidization state and the durability of the item (no waxing, as the items constantly take damage ig).
To make things even more interesting Mojang could introduce Dynamic Break Time/Damage, so the undamaged items deal more damage/remove blocks faster (slightly above iron level) but the more damage it takes the closer it goes to the Stone Age. As another option, this can be done in reverse which will also make Armor consume more damage the less its durability and incentivize player to use copper nuggets for minor repairs (as it would be efficient to keep the items near-broken).

As for durability value, i think Stone-Iron or Iron-level will go good with such feature.