You should build your elevators asymmetrically. Start a new elevator in every skylobby.
The SimTower-help provides information about the behavior of the SIMs within the tower and towards the elevators. It's always been a big help to me.
They never switch elevators more than two times or so. And you have to plan your transport in that way.
I always felt that it was a bit annoying that you couldn't arrange it in a logical way that has a system, but that you had to keep with the SIM behavior.
But I think that's realistic - in a way...
Hope that helps.
k: