I think it would be better just to remove all references to Google servers from Android code and maybe install Play Services while blocking them from connecting to Google (for compatibility with Play Store apps). I don't understand why they decided to rewrite UI wih C++. Is not Java easier to use than C++?
And as a result native Sailfish apps won't run on Android. I doubt there will be many people writing them if OS share will stay low.
Sailfish is nothing like Android, its a continuation of Nokia's old Meego platform, its built on the same tech stack which closely mirrors what you have running on a desktop Linux machine.
There is no JVM unless you install the Emulation layer yourself.
And as a result native Sailfish apps won't run on Android. I doubt there will be many people writing them if OS share will stay low.