Help with Z axis and THC upgrade

Hi there
Im in need of some help! i think i have done too much reading and am now going round in circles trying to work out what direction to take!
I have been retrofitting an old plasma table with a new csmio ip/a motion controller, X and Y axis are both working great now, but the Y axis was controlled by a separate standalone unit, called an Innerlogic rsvp 401hd, it was Y axis hight, auto voltage control and servo driver all in one box,
I cant get the voltage control to work at all, and am struggling to get everything to be timed correctly with mach 3, I would also like to have control of the Z axis with mach 3, and plan to do a rotary axis at some point so Z axis control would be handy!

As far as i can figure out so far, i could either; use something like a gecko G320 driver to power the original dc servo motor, but i would need to change the encoder as currently it is a 24v one, and the gecko needs a 5v encoder, and also i am not 100% sure the csmio IP/A controller can give step/dir signals as it is a -10v/+10v controller.

So it might be easier to just buy a new stepper motor and driver, something like this,
https://www.cnc4you.co.uk/Stepper-Motor ... o_Kit_4NmB

Or i have even seen whole new Z axis kits for not that much money, would be a shame not to use the perfectly good original one though, it already has limit switches etc installed

Initial torch hight was done with Ohmic sensing and i think by monitoring the current from the servo motor, would something similar be possible? i have seen you can get modules to do the ohmic sensing, not sure about the motor current thing though.

As for torch hight controller, i think i have decided on the proma thc150, seems like it would do the job and be reliable, any others to consider?

sorry for the billion boring questions, but any input is gratefully received!!
cheers