New thoughts:

So the trouble has been getting the triangulation to work. What if we upgraded the brain to a 32 bit controller like the bigTechTree SKR V1.3 with the bigTechTreeTFT35 to use as user input.

Next I wanted a cheap way to measure the distance from two points. My new thought was to use the Measure King. So I bought one and ... not amazing. It isn't a laser range finder at all but instead a sonic range finder so that won't work. But the string measure might work as a range of 11ft (ok with me). I would need to pull it apart and find a way to read out the measurement. Take two of them and put the two cords as close to the bit and as close together as possible (to decrease wrong measurements if the device is rotated). Next Make sure the string are a straight line to some arbitrary points in the upper right and left hand corners of the work piece.

I'll have to work on getting in the guts of a measureking. I also have an SKR on its way to my house :-).