I’d like to suggest a new type of lock, that doesn’t need keys, and which can only be locked/unlocked from the inside. It would ideally not use metal either. A wooden latch to a room, characters can go in, lock, use, unlock, go out. It would also be much faster to break than a metal lock.
This is more of a wish than actual need to fix something that’s broken.
I think this can help with metal balancing and still allow some slight protection in poor towns, but I wouldn’t even go there, I’m just tired of managing keys. Some public rooms, like baths, offices, meeting rooms, can very well be left unlocked all the time and could have a key on the ground or on a bulletin board, but those keys tend to disappear, people forget, it’s a nuisance. So a door latch would work wonders. Please and thank you.