I'm going to throw this in here just in case you have the "bush" flag on any of your tiles as the "!" won't allow any characters with that to use bush depth. Then you won't have to add "!" to your player.
class Game_Player < Game_Character
def shift_y ; return 0 ; end
I just saw in a manga an interesting mechanic - setting up a stationary teleport beacon that one can go to no matter where one is in a dungeon. I think it'll work with a similar setup to how I did my airship transition.
Ooh what if you could set up multiple beacons and choose from a list of the beacons you set up?