The restrictions in every ecosystem are just stupid.
A few days ago we wanted to play the same music from Spotify on both the iPad in the kitchen and the living room (Mac Mini and other options). Not possible. Ended up installing AirFoil on the Mac and streaming the music from the Mac in the living room to the iPad in the kitchen. Works like it should, you just click all the destinations (AirPlay-compatible) for the audio.
Sorry Tim, Jeff and Sundar but I want a full, interoperable mesh. If you think you know what I want, you are wrong. If you think all the devices will have the same logo, you are wrong.