Seriously, what do they accomplish? They just take up inventory slots and are nothing but a liability, and a lot of people don't even build gates for that reason. If it was possible to just replace the lock on a gate I could see them working, but having to bash down and rebuild your gates every time someone with the keys gets killed is a bit ridiculous.
Anyway, I can understand if you want to keep them for key-stealing purposes, but please keep them away until you've made key rings and replaceable locks.
Instead of keys, just let people who have trespassing rights on a claim open and close the gates. It's not like anyone builds unclaimed gates anyway.