Spindle Control, using Hydraulics?

Would it be possible, within reason to control spindle speed with a
hydraulic unit?

On my Lebond lathe the electric motor turns a variable displacement
hydraulic pump that drives hydraulic motor, which turns the
spindle/chuck.

I wonder if a stepper motor could move the stroke control for the pump
in a closed loop feed back system using Mach3 with a signal from a
encoder on the spindle?

Daniel T. Medlin