[fensgrim]

I had plans to do such project for exactly same reasons since, like, 2011..

Wanted to have pulseaudio/alsa dmix handling multiple streams/mixing them out with a help of dedicated hardware BT/DAC-ADC-BT path, with a goal to have smart handling of voice calls over music on the go, fake 5.1 in the room, and a voice enhancer / fast rewind for call streams..

Then, Volumio took enough of the raspberry-based hifi market (despite having no bluetooth support, lol) that I've declared these plans no-go as investing in this solely for fun wasn't that enticing, compared to just getting a spare set of equipment to separate work/home audio.