I like the idea of beeping noises for when the elevator. And instead of switches for controlling up and down you could use a gui menu that looks something like this.
And in the rooms it would be nice to show what floor the elevator is on, and the same goes for the inside of the elevator. So if you're already in the elevator you could know when some one is about to use the elevator. If you're not in the elevator you would even know what floor the player went on.