If it helps with a difficult decision making, I'll offer my views on what i believe a sonos plugin should comprise.
I think the basic functionality of play, pause, next, prev and basic volume control are key, along with switching to line in and to the queue.
I would add Terry's two points as nice to have.
Whilst not necessary for me, I think current and next track info, including album art would be icing on the cake for others.
A plugin with those capabilities would be complete.
Looking forward to testing the update. Once again, thanks for the hard work. It's being used every day here!