The problem is, what program?
How do you run it, how do choose what to do with it, how do you run the user interface?
Remember, for many (most?) of us, the Core that would accept this 8nput is running on a headless Linux box in a closet in the basement.
A viable solution has to run a program on the remote, maybe an iPad or Android device, send the signal back to the Core, do its thing (multi-zone sync, DSP…), and then send it to the chosen endpoint, most often not that same iPad.
That is the Roon architecture. We wouldn’t want a limited solution that worked only in some configurations.
Possible but not trivial.