GPIO Buttons Plug in and Multi Room Support

I am hoping to build a “remote control” for my Volumio devices. Had the idea of a Volumio instance on a Pi with touchscreen and buttons but no audio output, and using the Multiroom tabs to control each device. I then added the GPIO Buttons Plugin, and was hoping that the buttons would control whichever remote Volumio device I had selected. Unfortunately, they only seem to control the local device.

Any ideas how to get round this, and could it be a feature request?

Many Thanks, Anthony