Hi Rich!
Sorry for the delay on my response! I'd thought I'd responded!
However, the folks at Shapeoko are trying to be as helpful as they can, but they emphasize that they do not support equipment that is not their own.
I guess that is a reasonable approach, given that most Shapeoko owners are probably not familiar with Mach3.
But, all things considered, it would seem that a Mach3 operating option would be a great selling point!