The locked doors in the Horror maps have a revolutionary feature that I've never really seen anyone talk about. This of course, being that their state (whether or not they're open or closed) its client-restrictive. Gameplay-wise, this means players have to collect keys and unlock the doors themselves. If not, they're unable to go through, even if another player has unlocked the door themself.
I think this feature should be further explored, as it brings puzzle maps/worlds to a different level with players being deliberately required to do everything themselves, instead of relying entirely others. Adding buttons with this feature would be a good start.
The way it functions is simple- Whoever presses the button (be it by hand or by gadget on-hand) sends a signal (specifically tied to their device) through the wire and perceives it as normal. Any other witness, however, sees none of it happen, unless they activate the button themselves.
As a person who is currently striving to make a puzzle-centered "horror" map of my own, I feel this addition would help make my experiences less cheesable (which is something I fret about often).