Rhythmbox as a UPnP renderer/controller

I have been playing with UPnP recently, and been using the gupnp-av-cp
tool to control stuff. But this seems really clunky, not surprising as
its really meant for testing. So I was thinking of rhythmbox
controlling renderers, as in when you play content from a media server
in rhythmbox, you can also select an alternative renderer.

I found this https://code.google.com/p/rhythmpnp/ and
http://coherence.beebits.net/wiki/RhythmBox , but neither act as a
controller? I have also been told that rhythmpnp is not built for the
current plugin infrastructure.

So, does anyone have any advice if I want to try writing or expanding
an existing plugin to allow rhythmbox to act as a UPnP controller?

Thanks,

Chris