OMG! Beautiful! I want these for my Les Paul!!
I am intrigued by interesting challenges (plus I love anything with stings). Now that I know what you are trying to accomplish, I am ready to tell you that it is doable with Mach, no problemo. I know you are noodling around with this, but if you do not arrive at a satisfactory solution, and you are not in a terrible hurry, then e-mail me directly and I'll help you with the solution. If you find a solution, please post it back here.
This has my wheels turning. If you are not moving your tables during the operation, could you make temporary use of one of the other axis to operate the 4th axis . . if you had a way to instantly, automatically, temporarily and transparently switch them back and forth? In any case, I'm pretty sure we can create a macro that will turn the axis 180 degrees with a single M code.
i.e.
G1 (blah blah blah make the part)
M5 (turn of spindle)
{vacuum, collect, advance stock, other cool stuff}
M981 (rotate axis 180 degrees)
M47 (do it all again)
Where can one see pictures or videos of this very interesting machine of yours?