Z'dude -- The goal is 20K feet of climbing without doing the same thing twice is, at the very least, an interesting thought experiment.
Since going uphill is easier on the body, at least an old body, it is tempting to use the tram to go down. If the tram is allowed, are we allowed to use a car to go from place to place?
1. Standard C2C (~10500')
2. Ski Hut Trail (up and down, ~4000')
3. Bear Flat Trail (up only, 6000')
Why one way on the Bear Flat Trail? Because you are allowed to die on top of Baldy and be carried down in a plastic bag.
Alternatively, you could combine C2C with the San Gorgonio 9 Peaks Hike. The right choice of route could get you close to 20K feet.