Mute snapclient when another stream is using the sound card/local Mopidy is playing

[daniele-athome]

I'm more looking for ideas here than a proper feature request.
I'm using this configuration for my multi-room setup, so a central Mopidy + Snapserver is installed on my media center and speakers have snapclient + their own Mopidy instance for single-speaker use.
However this type of configuration becomes messy when playing both from the central Mopidy and the local (speaker) Mopidy. I would like to mute (or disconnect) the speaker-local Snapclient when the speaker-local Mopidy starts playing and unmute (or reconnect) when stopped. I figured I can do this in 3 possible ways (triggered by a custom Mopidy plugin that I'd have to implement):

1. stop/start snapclient service (con: requires systemd privilege, possibly root)
2. use some sort of alsa configuration (e.g. softvol) so I can mute a loopback device used just for snapclient (con: complex alsa configuration)
3. contact snapcast server and ask it to mute/unmute that speaker (con: useless round trip, basically asking outside of localhost to mute localhost)
4. control snapclient from within Mopidy (instead of being a separated systemd service) so I can stop/start it at will (con: none?)

Am I overlooking something? Am I overcomplicating the matter?

P.S. sound card shared access between Mopidy and Snapclient is not an issue since I'm using dmix.
P.P.S. I'd rather not install a snapserver in the speaker just to select the stream (using a meta stream)

[daniele-athome]

For anyone that will be reading this, I made a Mopidy plugin that controls its own instance of snapclient: https://github.com/daniele-athome/mopidy-snapduck/
It's been working pretty well, I'll be publish it on pypi soon.