We have a Master key that's used to open door both ways.
then a slave key to open it one way.
Why not an attendant key that can open the door both ways but can not be copied or be used to change locks.
I can see the augment of this being a problem with some pvp.
But honestly should not be to much of a problem.
if it is. make the key only work for visitor gates and stone/stick fense.