In general it is pretty easy to upgrade a Multicam machine to a new controller. The drives and sensors use industry standard voltages, so are compatible with most retrofit packages. I would take a look at the Dynomotion Kflop controller.
It does look like your spindle drive is currently controlled by a RS485 serial communication signal. But I'm sure it will also take a standard On/Off and 0 - 10V analog signal. Would require a bit of a change in the drive programming to implement, should be very easy to do.