I ended up going with an RMC3 being a middle man.
I hooked up the IPCP 550 and RMC3 via RS232 and used the universal projector rs232 bidirectional driver.
It seems that the RMC3 isn't at all picky about syntax and reads the user defined string exactly as it is written in GCP, but it seems that there is some translation issue from when sending signals from the RMC3 to the IPCP550.? Even though I specify the exact "input status" strings(I get 10 available to preset in the GCP driver) in the same format as written in the simpl program, it just gives me an "invalid command" error when tracing Extron toolbelt.? I think there are some added bits to the signals from the RMC3.? But that really isnt a big deal yet, as it is just to send feedback to the controller for button press confirmation.? Though it would be nice to use the status fb signals to feed back into the Extron processor so that I can have the buttons be disabled/hidden when the nvx endpoints are nonfunctional.
Otherwise, this has been very reliable.? I am just using serial sends to the XIO routing "video out" signal to change the subscribed stream.? I tried everything else under the sun, but this was the most reliable way.
I sent this over to my colleague. I hope he is able to use this information, worst case if he needs a spare Crestron processor I have one to send to him.