Hi Steve,
My recommendation would be to modify the ethernet driver to support this feature or discuss with Renesas/EL to do non recurrent engineering.
You don't have to use the configurator to set up the NetX interface, its easier done from source code (see the NetX manual), I would start by studying the driver files to see how they work what changes to make to get this to work. Feel free to ask me any questions about the workings of the driver.
Stefaan