You might wanna try adding your internet stream as a "radio stream" (using directshow as music player, BASS won't work, I guess). This sounds a bit weird, but that's the only way you can get it running at the moment. The video player doesn't offer many features then, but if MP "understands" your stream, it plays at least.
Play around with it a bit, not all streams work, try various ones.
This is a "workaround" until there's a proper implementation for streaming media.