I am running a split system with both S1 and S2 devices.
I can start any of them, and then turn off my app or computer, and the device continues to play (with the exception of the shared music library from the computer, only because the shared directory disappears from the wifi when the computer is shut off).).
This fact proves that the device is doing all the work, not the S1 or S2 apps/controller, which simply send the device an instruction to begin playing whatever service, while the device takes it from there.
This proves that S1/S2 total incompatibility need not be a foregone conclusion.
Both my S1 and S2 devices play identical services, some simultaneously.
There is no reason my S2 app should not be able to tell my S1 device to start playing a service it already is capable of playing, especially when the S2 app sees the S1 device in the setup/detection process before it decides to error out and inform me the two are incompatible.
I understand that some feature might arise in the future that S1 devices cannot handle, but for now that feature does not exist.
Having both types of devices simply play in sync seems a rudimentary clocking thing to do, and if a device doesn't support a service the app could simply tell you. This could also save the company time by only having to support one app.
Please add the ability for the S2 app to command an S1 device to do what both can already do...