You could certainly propose it to them (especially with a PR that includes code), or patch it into your local copy if they decline. I wouldn’t be surprised if Google wouldn’t allow that in the Play Store-compiled version of the app, but I don’t know.

Yeah, I think it’s quite common to have a “Google Play version” and an “F-Droid version” with different implementations behind build flags. Not sure if it’s required though – I can see some UnifiedPush providers in the Play Store, at least.