Thank you so much for this!! The state of the Android Spotify app is pretty sad and I don't see it changing anytime soon (there have been threads requesting this on their forms for years).
The only other feature I really want and don't expect to ever get is audio ducking (lowering the volume when you get a notification or your GPS alerts you of a turn similar to how iOS or Google Music acts instead of simply stopping the music, which is really annoying). Apparently using "AUDIOFOCUS_LOSS_TRANSIENT_CAN_DUCK" allows Android apps to lower volume during a brief loss of focus. I was wondering if you know of anyway to modify the spotify apk to do this as well. There is more info on this function here: developer.android.com/reference/android/media/AudioManager.html
I attempted to add this, and I've got the apk decompiled but that itself stretches the limits of my knowledge and I have no idea where I would put this command inside the app.
Regardless, thank you for picking up the Spotify slack and providing continued updates!