Gundog, with all due respect, I admire your ingenuity, but that's simply too complicated and too much goofin around for me for something that's so quick and simple to do by hand.
Sometimes I rough them in on the drum sander, but more often I do it all in the bench vice with hand tools and in my opinion, it's one of the quickest and easiest aspects of making a bow. I like my jigs and machines too when they're warranted, but sometimes they can place unnecessary obsticles between me and my desired results.
The cross-section of my trapped bow's limbs is not only a very 'general' trapezoid shape because it doesn't have angles and flats(other than the flat surface of fiberglass, but I haven't made a glass bow in a few years)... backs are usually convex bamboo and bellies are always radiused... the sides aren't ground flat either, they're curved outward. Additionally, the cross-sections are in a continual state of change from dips to tips, so I am making CONTINUAL freehand adjustments to how I hold/turn the bow and/or tools as I run them up and down the limbs. To try to replicate it with a jig or basic machines, I fear, would ultimately prove to be an insurmountable task and not worth the trouble... and I'd likely end up having to make adjustments by hand anyhow.
Like I said, I certainly respect the ingenuity though and I love a good jig as much as anybody :^)