I think It'd be interesting for certain survivors, thinking like Joe and Barb, to be able to repair weapons for maybe 25%-50% of their durability at the cost of some supplies. (duct tape, screws, wood depending on the weapon) To keep it balanced, maybe only once or twice before you can't anymore.
I think this could be interesting as in real life, if you had an axe that was very clearly about to break, you could duct tape that thing so it lasts a few more hits, or tighten a handle on something etc. etc.