Hi Voicecoil.
If I understood right from what you said, a DRO unit is just an indicating unit. It is not a bad ideea, but I am inclined to attemt to make a magnetic device with a dial indicator on top, or something far more simpler (I do not know what yet :P) that serves the same purpose. I'll keep in mind the ideea. There are a few unit on ebay that can indicate 2 axis, and come with glass scales, around 200$ + transport. The approach it different from what I had in mind. (one home switch that zeroes the blade, and then a metric command given to a motor), but it might still work. Thank you.