UPnP contreller+renderer app for TV and win8 modern UI. That way could be as solution for use of MP on non MS or difficult to build full MP client platform.
I recommend MP 2 have a windows 8 client as part of its initial release. The client side of mp would be "fairly" easy to port to a windows 8 app due to them both using the same ms technologies. Most of the heavy lifting in mp2 happens server side with the client acting only as a gui. That would fit perfectly as a windows 8 app.
*cough* *cough* - newer say easy when you aren't 100% sure. Porting the Directshow based components will be a huge task. Any volunteers for converting all the Directshow filters into MediaFoundation filters? Remember to port LAV splitter, video and audio decoders as well
There are even guides on pointing out what needs to change to move a .net app to a windows store app. Media foundation support isn't as desperate as you make it out to be. Mediaportal itself has been supporting the Media foundation powered EVR renderer for a good while now. Media formats like h.264 are supported by Media Foundation natively. 3rd party filters for other formats also exists to add support in Media Foundation, just like how directshow gets most of its support.
I know that the tsreader and the audio render take a lot of work, especially since directshow is being fazed out.
It will be a big work but has to be done.