The main problem with elevators today is that you can only have on cage per shaft. You could solve this if you could have multiple cages per shaft. A bit like

The main problem with elevators today is that you can only have on cage per shaft. You could solve this if you could have multiple cages per shaft. A bit like how trains operate with switches and passing points. I imagine that would take some serious technical development but doesn't seem entirely out of this world. It would be easier if you have cableless lifts like the maglev lift Toshiba developed (http://www.toshiba-elevator.co.jp/elv/infoeng/technology/tec05.jsp http://www.toshiba-elevator.co.jp/elv/infoeng/technology/tec...).