A part-answer, sorry.
Even though I can’t make out any dimensions on your drawing, from your description of an open tolerance and finish, this should be easy, Kev.
Not knowing quantities, I'll assume this is a single-part. (Production quantities may differ) While copper-tungsten rod will wear less, it will cost more and the lack of flushing can become problematic. Again, without knowing the diameter, I’ll throw darts blindfolded and suggest using a coreless copper tube for through-hole flushing, using spindle-rotation if available.
Without knowing the finished hole diameter, I can’t suggest an electrode-size or overcut, but I’d go with an electrode small enough to allow you to go in “hot”, while still leaving stock for clean-up and straightening via your orbiting feature.
I don’t know your machine, but for Cu vs. Cu; you must use a negative-polarity electrode and high-frequency generator settings (carbide settings are a good start if you have them). In this combination, electrode wear will be high – at best, a minimum of 100+%, depending upon your settings, but tubes are cheap... time is not.
In your case, EDM is short for, "Eat Dat Metal". With little chance of failure or scrap, I'd say "Go for it" and let us know your results. "What you learn on your own, is often better than what you are taught" - BG
Seeking more and better advice from the rest of this excellent forum... if anyone else can actually see the drawing-dimensions and can offer better-founded advice, both Kev and I would appreciate it.
Bud Guitrau