What about this for an add-on box for rotary engraving?

Just need a couple of 8 pole double throw toggle switches and some easy driver stepper motor controllers if you were to build it yourself.

I’d really love to hear any constructive criticism of the idea / design.

For the steps/mm you only have to do the calculation one time, once you know what steppers and gearing between the stepper degrees per step and pulley ratios. Once that is done, you just scale your Y axis by that ratio of current steps/mm to new steps/mm and you have your scale to make it come out correctly proportioned. A simple Excel calculation with the diameter of the round object as the input should give you the correct scale factor, and you are set…