Great, I think it would be interesting to add more push adapters for Android devices that are not using Google Play Services, so that Parse Server becomes out-of-the-box compatible with pushes from Huawei, etc. Once you are working on your push solution, maybe there are some learning that we can incorporate into Parse Server and the Parse Android SDK.
Currently, Parse Platform is pretty dependent on Google Play for that matter, and I think it would be good foreseeing to loosen that grip. Not only for apps in China, but also for users anywhere who refuse to use Google Play Services due to privacy concerns.