I have several speaker systems in our house and none of them is connected to each other. What I do have is Spotify family.
I would like to control/connect several family profiles through any of the profiles. In this setting a song would be synced and played on all profiles.
That way I could make my speakers "smart" and I would have a multiroom system without having to replace all my speakers.
Any of the connected devices (ipad, iphone, computer and android) would choose to be a part of the system or not.
Say that I would like to use my son's speaker I could. But if he wants to be alone with his speaker he would just disconnect from the rest and listen to his on music. Maybe even have a function to look a device, so that it couldn't be possible to reconnect that device.