Seems legit to me - a bunch of robots on the elevator that are each responsible for perhaps ten kilometres of travel, and they pass the parcel to the next one i

Seems legit to me - a bunch of robots on the elevator that are each responsible for perhaps ten kilometres of travel, and they pass the parcel to the next one in line then move back down. You could launch way more things in pseudo-parallel that way. Or just an up line and a down line like most cable cars.