Background playback for unsupported-by-Media-Foundation files will come with Windows 10 RS1 (Anniversary Update) and VLC compiled for that version of Windows, not before.
The code is here: code.videolan.org/videolan/vlc-winrt/
There is a README file, and you contact me, should you have any problems when building the app.
I'm trying to do a Zune SmartDJ - like feature on my spare time. Maybe it will ship one day, but it's hard to do and the algorithm should be hosted on the cloud, tbh.