Think of the cable as the spine of the system. It stays stationary. The cars crawl up and down structures fixed to it, or are raised and lowered on their own much lighter cables, much like a regular elevator. A counterweight is probably mandatory, for dynamic as well as energy consideration, but it can be a returning car rather than a dead weight.
When 20,000 pounds goes up, 20,000 pounds must come down. If frictional losses are considered, even more must come down than goes up. Good idea? I am having trouble managing a clear idea of how the counterweights will work. It's very complicated, especially making adjustment for the change of weight as the distance from ground changes. Stages? One stage a mile?