This seems like it would be great to release as a library. That might increase adoption.

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)

Agreed, but I trust my email provider to provide push. I would be willing to block all the rest.