I've not played with it yet - but since you can draw on a screen panel, I had wondered about making my own tool path display in Lua?
I also have a C Axis and (once I build it), live tooling. There isn't much support for either, natively, in Mach4 (it's a bit unusual on 'hobby' machines) - but it strikes me, the tools are probably there to implement a solution.
It will have to wait for my next spell of time off (between films) though.
Si