That could work. Have tubes of air that have compressors every couple of hundred feet that shunt air in the main tube, propelling the elevator up or slowing its fall when it descends. The main tube would serve as a return. .I would guess that Endtown itself is depressurized. If it was wasn’t, the pressure of air under gravity would be about 17 and a half psi. While people can probably do ok long term with that, it would be interesting to see what would happen. Mines don’t go anywhere near that far down and the deepest ones in places like South Africa have to have compressed air pumped down and air conditioning because of the high temperatures.