Scott, this is probably overcomplicating it:
Rig up a sturdy table behind the lathe, and bolt a template down to it, with a straight edged plate on top, the plate being fixed independently of the template so the plate can be moved without disturbing the template. Fit a finger on the back of the cross-slide, so it bears on the template and straight-edge. Start with the straight-edge positioned so that only the "peaks" on the template are exposed. Take a cut, traversing the carriage with one hand and using the other on the cross-slide handle to keep the finger in contact. For the next cut, move the straight-edge back a bit to expose a little more of the template. Repeat, moving the straight-edge back a little bit more, and so on until the troughs on the template have been fully exposed. Then start on the next piece of stock, and carry on until boredom sets indo it all over again.
A more sophisticated table would have a feedscrew to take it, with template attached, a little further way from you between successive cuts. That would avoid fiddling with a straight-edge, which wouldn't be needed.
Andy