I was able to make the auxiliary table using my bandsaw, oscillating spindle sander and tablesaw much faster than using the CNC. And since it was a one time project it made sense. Having said that your design is now available to anyone who downloads the file. Thanks for sharing.
I have seen the Izzy Swan video about the extension. He sells the plans and/or the actual device. However he made an announcement on his youtube video he was retiring. So not sure if he is going to keep selling his stuff or not.
For me some projects are good on the cnc. I made a fence for my incra miter gauge with multiple holes so as I wore out one slot I could move the fence down and keep using it. But some projects are just easier to just make without the cnc.
The advantage of the CNC for the fence was on a drill press you have to move the material and can introduce mistakes. By cutting on the cnc I get exact placement of the holes and recesses.
Another thing I use the CNC for is making butterfly/bowtie inlays on projects with cracks/splits. I dont cut the inlay on the cnc because the project is too big to get on my XXL but I make the template that I use to cut with my router 1/8" bit and router guide bushings. I can make any shape I want on my CNC and dont have to rely on someone else’s template.