BP II duplicator conversion

Advice please...I have access to a BP series II machine with the x,y,
and z axis all driven by hydraulic motors. The motors are controlled
by a device I am not familiar with but strikes me as being like a
digitizers with a probe. Push the probe in certain directions drives
the x/y table and the z axis. All axes have ball screws and nuts.
Since this machine is a reasonable buy, would it make a device to
retrofit for CNC?? The hydraulic motors are about the same size and
position as servo's driven BP mills I have seen. The motors appear
to be driving a pulley/belt rather than direct drive. The z axis is
the knee of the machine and not the head. I wounder if servo's would
be powerful enough to move the knee up and down (I don't believe that
the knee has a counter weight system) In place of the machine head
is a long slotted plate for mounting multiple machine heads. The
hydraulic controller is also mounted to this plate. Any advice would
be appreciated. Thanx...Richard in Michigan.