This past week, I've made a lot of progress on this machine.
I replaced the hubs - not quite as shown above because I found a much simpler way: keyed shaft stock.
I also made a set of rails for it to roll on, which will eventually become a complete table.
I bought some proper cutters, but not left-hand turning cutters.
I still plan to use the cable system, but currently not using it, and I have decent results without it, actually.
Today I turned out a reasonable copy of an arbitrary 2D shape. Later I will try it on some 3D shapes but I need to set up proper fixtures for doing that.