I wonder if fastmail could be persuaded to put in a different endpoint for their app. They already have the infrastructure in place to run servers, and take a privacy stance. Not having to go through google would probably make them happy.
Obviously it would have to be optional, but little cracks in the door.
There is a massive technical benefit for all apps to use the same push server.
If many different apps use their own push server, a connection has to be kept open to each and every server, and each open TCP connection costs quite a lot of battery (since the system has to wake up to receive keep alives)
