I only see one unidentified data point in the ARMO record structure. Could be durability... could be something else. Didn't check WEAP.
There are several "Condition" GMSTs for armor, weapons... and guns. Obviously Fallout leftovers; whether the ones that might be relevant are still hooked up is anyone's guess.
What could be used, is keywords. Rather than a smooth numeric transition, it would be simplest to have a set of specific condition levels (e.g. undamaged, used, worn, damaged, useless) and a very small random chance of moving down one rank after a hit. The existing keywords include material types, so e.g. dwarven could be configured to take a lot more use than glass.
Incidentally, KhadirgroGhurkag: Phitt is right about what could and couldn't be done in Oblivion, and why. Inventories are implemented as a list of FormIDs with some extra data, including count: six longswords in your inventory are represented by only one longsword entry, and the number 6. Enchanted items are implemented by creating a completely new form, not as a modifier to the base. Furthermore, the "associative map" type you started the debate with doesn't even exist in OBSE. People have repeatedly asked for it, but it's not feasible because FormIDs outside of Oblivion.esm are load-order specific, whereas saved games are not.

But I agree that your idea is a good compromise.


