What if the locking used levels the amount of levels the chest had the stronger it would be, so the thief had to be a higher level than the chest to lockpick it with a golden hoe+ he would loose his levels on lockpicking it.
If the lockpicker had less levels than the chest he would loose all his levels too.
The locker of the chest would losse that many levels he would choose on the chest.
This could be done with a spout gui.