Here’s a diagram from the patent application for a cone-drive CVT used by ABC (1905-1910). It’s fairly elegant - the drive control engages the center cone, and a tension system holds in the driven cone as the drive cone extends.
I think this system allows for a little more power transfer than the simpler one used by GWK, and certainly lower wear. It also in theory allows full speed in reverse... though as this one is configured, you’d have to maintain reverse tension manually, and the driven “normal” output cone probably bottoms out somewhere. You might get to 80% full forward speed before the drive cone hit the reverse cone and the normal driven cone at the same time... which hopefully there was an interlock for, or should have been, as smoking both of them would be bad. Even if driving 30mph backwards is dumb in the first place.