Hi Squarewave,
I may be able to help you . I have done some mills and lathe retrofits and want to become a CamSoft retrofitter. I admit I have never done a 4 axis EDM, but I have researched the EDM features you need in the CamSoft manual and CD. I found a EDM interface with logic for Spark gap control reading real-time analog voltage. Plus I found logic for the other items on the CD like fluid on/off, automatic wire feeding, wire cutting, spark gap voltage and epack or power control parameters are there too.
It's real easy to configure the operator interface to 4 axis U,V and set up the motor specs. They can do 8 axes of coordinated motion with all types of motor types and feedback devices.
What you need is almost all there. I could help you and I don't charge much. Are you near Chicago? Do you have CNC Professional or the Lite version?
Jim