Doug, a few months ago I looked long and hard for a CAST ACRYLIC insert that was roughed out . Nobody is making anything like it that I could find.
Based on my research a rough turned insert, with just a pilot hole that ended well before the tennon ends, would be a very popular item. I ended up having a mess of them custom cnc'd for me and I love them. I still do the drilling and of course cut the tone board radius. I believe you could sell a roughed out insert that was just a 2.5” X 5/8 dia tennon on a 1.75” X 1 3/8 Dia tennon with a pilot hole and no profile at all. A call maker could slap that puppy in a collet chuck and finish it up in a fraction of the time it takes to start from scratch, and, still have a custom call. Having a pilot hole is a big help and allows me to do the finish drilling on the DP with no worries, and the tone channel is always perfectly centered (that's huge!)
I hope you find enough interest in this to keep you moving forward !