I have the unit hooked up to an older amp. It would be good if one of the gpio pins on the Pi could be used to turn the amp on (or off) when the Pi is playing (or not) . When off is selected the only way to get it going is to repower the Pi. But if when the pi is paused or stopped (for a time) it would power down the amp (via a suitable interface from a gpio) and when play is pressed it would turn on the amp (via gpio interface).
Needed pretty much the same thing - but I really needed the delay as my chain consists of a tube amp, and didn’t want it toggling on/off each track change.
I have a submitted a PR to add a delay setting for the original AmpSwitch plugin so feel free to test it out! 
I also managed to add a few lines to code to the underlying python based spotify-connect-web of the vospotconnect plugin now to have all my bases covered to toggle the amp from Volumio!