Using the Spotify Rest API it is already possible to build nice feature rich Spotify clients for remote players. I don't think there is a supported native playback library? I'm not sure how local playback is implemented in this project.
The main problem I have with the Spotify API is that its remote playback management API is limited/incompatible with some players (Sonos).
The main problem I have with the Spotify API is that its remote playback management API is limited/incompatible with some players (Sonos).