could this be done

I have been looking at lathe threading and been thinking
instead of using encoder feedback with limited options ah-ha,
microkenetics
and expensive at least to me
could a lathe be setup with a aux servomotor drive on the spindle with
a gecko drive
with a quick release belt drive or contractor to switch between
spindle motors when you want to cut threads
assuming no backlash ball screws and gecko servo drives

could a program be written that would when used with this setup
that would output the code
that you would input your machine parameters and thread info
length of thread and pitch, thread depth thread type ect.

and have it cut the pitch and then back up along the thread to start
infeed the proper amount and repeat
you would not need a big servo motor on the spindle as
it would be "geared down" a bunch for finer resolution and you don't
need much HP or rpm to cut threads anyway you could cut multi start
with this also
I have no idea about programing this might be a nightmare
mike