Integrative Audio/Video Player App?

In the windows app store there are a lot of different audio and video player apps, some of which are pretty nice and useful. What I would like to have though is a player that can access audio AND video content from SEVERAL sources (for example: local music and video library and local drives, YouTube, skydrive, ...), and that lets you create playlists that consist of content from different sources. That way I could just open the app, select a bunch of songs/videos that I feel I'm in the mood for, no matter whether they are local files or online content, press "play" and enjoy, without having to switch apps/sources.

That would be really useful for people like me, who like listening to music while doing other stuff.

Is there such an app? What about developing one? ;)