So, if you're writing your own RPG version of the proxy, then you have to do all that bundling and unbundling. Then you have to invoke the target service. I, however, skipped that. Since I have control over all the pieces, I extracted the actual business logic and re-wrote the target service to call the business logic. Then I added code in the proxy to call the business logic directly.
It's not quite as complicated as it sounds and it works really well as a proof of concept. I can now say with certainty that it is entirely feasible to write a complete, Java-free EGL Rich UI application, using only RPG as the back end.
I'll clean up the code and export the project (including a savefile with the RPG code) in the next day or two.