Thank you internet! This is really cool, just like I pictured it :)

My living room RPi based music solution is an old Grundig radio from the 50s, modified so I can control the volume using the actual volume control. Playback sources (currently online radio stations chosen by genre) can be switched using the physical buttons. The "off" button shuts down the Pi.

Maybe I'll do a writeup on my blog sometime, in case people would be interested...