It would require you to remove them as surrounds and grouping the two rooms together, resulting in a delay between the Plabar and the rears due to buffering.  You may or may not notice the echo caused by the delay, but it will be there (drives me crazy because I’m sensitive to things like echoes and lip-sync problems). 

Thank you

Unfortunately, Sonos does not provide a system to assist the ‘hard of hearing’ folks, at this point in time.
 

Note the quotes I used, not all those who might appreciate such a development have actual hearing issues, there are other situations in which it might be helpful. 

We are asking this to Sonos since long time, i am convinced they will never implement this unfortunately...

I set up the new Atmos with a sub and two [play 1’s> How do you include the rear speakers in the overall sound. Are they automatically adjusted with volume changes?

Cheers

John

Have you gone into the settings for the Arc and added the Ones as surround speakers?

I'm not sure what exactly you mean by 'include in the overall sound '