Depends on what you consider ‘easy’. Basically, each time you want to ‘switch’ the Sub between your Arc’s room and the music speakers (the Architectural set, not set up as Surrounds, but as a different ‘room’ in Sonos), you basically have to set up both rooms each time, there is no easy way to ‘switch’ the Sub between two rooms. And if you use TruePlay, you’d lose that every time you reset. 

Were I you, I’d likely set the Architectural speakers as surrounds for the Arc, leave the Sub connected to the Arc, and use the ‘Full’ setting for the surrounds, so you get the complete stereo sound from the Architectural speakers along with the sub, and just turn down the Arc, even though it is ‘playing’ at the same time. 
No need to switch the rooms for the sub, but you do end up with the Arc playing music when you’re playing the Surrounds.