There are perhaps a few things to consider with this suggestion. 

The Sonos Move would likely present other issues when adding and removing the speakers as surrounds, which I guess might only take a minute or two to bond/unbond. 

BUT... each time a user makes a change like unbonding/bonding HT surrounds, they’re also losing the trueplay tuning of the room and that will take several minutes to do again for each room.  Also, if using the Move for Alexa or Google Assistant, that assistant will get removed every time they’re setup as surround speakers, so they will not work for voice when used as surrounds with the Beam, or Arc etc. The user would likely have to go through the voice assistant setup each time too.

So personally speaking, I can’t see this being something that Sonos would want to consider. The experience for an end-user would be quite problematic and to try to simplify the process would likely involve a fair amount of software development cost with little added-profit in return for Sonos.

Thanks for taking the time to share your thoughts. 

I agree that accommodating my wish would not be in the best interest of Sonos from a bottom-line perspective so why would they accommodate my wish? I imagine it would be better for Sonos if I would purchase 2 Sonos One SLs and dedicate them to surround sound, but ….

as one for whom movie watching with surround sound would be an “event”, I am willing to accept all the inconveniences you list. So...would it really be a heavy lift for Sonos to allow using a pair of Move speakers as surround speakers if I’m willing to go through true play tuning and assistant set up before and after each use? The Moves are going to spend 99.9% of the time on the deck when it gets warm (they hang out in my office during the winter) so either way, they will have happy lives.

Thanks again for sharing.