I would like to see a second keyring added. One for the keys in the game. This way as you find particular keys, you can add them to the ring and keep them forever. If you want to make it harder, limit the keyring to only 5 keys per ring or something.
I know they respawn in their locations, but I just think it would be fun to pull out your keyring and have your key. After all, who drops a key after using it?