Also got rigid tapping on my BP
Works well at lower speeds as its only a standard motor not servo drive so if you go too fast it will over-shoot but not been an issue yet.
It also has two spindles, one goes to 24k. All controlled with the same control cabinet, i fitted as many bells as i could when i built it
Yes the VFD outputs it as a signal IIRC and that goes to an analogue input on the controller.
Junk rebuilder VMCs seem to have dried up now, as you say they are all 5k plus, then you need 5k on controls/rebuild and thats if the ways are not shot.