@marijnzwemmer: If you haven’t done so already, make sure to check out the Media Framework. I think it would be great if your player was a plug-in. We considered integrating ffmpeg ourselves, but weren’t able to because of its license.
If you put your code on GitHub, it will be easy for others to integrate changes or fixes back into your code.
I also think that playback without audio is still useful for certain use cases. Pause, Restart and Seek would probably be quite important though.