It appears that I can make this happen by using the STAnything platform, an Arduino or similar supported microcontroller and the wall touch panel.
The wall mounted controller would operate as normal, setting the output terminals to whatever combination of values would create the appropriate color requested. The signaling from this would run to several input pins on the microcontroller via some small electronic circuits to step the voltage down, instead of to the LEDs. The microcontroller would operate as the lighting master for the LEDs using some output circuitry to actually drive the LEDs.
STAnything would operate the LEDs, listening for inputs from the wall controller… When the input values change, the wall controller overrides the STAnything settings and the microcontroller reports back to SmartThings with whatever the new values would be based on the input. Change a setting within SmartThings, and STAnything takes over again, ignoring whatever settings are on the input pins… Until/unless the input values change from the wall mount controller.
Sadly, this is well above my abilities with regard to programming anything, but it’s likely the only way to make what I want happen.
A friend and I brainstormed it. He has microcontroller programming experience, but does not have time to delve into it for me, so I figured I’d post here and see if anyone was interested in trying this out with me?
I have the hardware already, just need to build some opto-isolators for the inputs.