Play audio file stream using HTTP Live Streaming on iOS client without losing UI to Quick Time

http://developer.apple.com/library/ios/#documentation/MediaPlayer/Reference/MPMoviePlayerController_Class/Reference/Reference.html

The docs say:

Playback occurs in a view owned by the movie player and takes place either fullscreen or inline.

In iOS 3.1 and earlier, this class implemented a full-screen movie player only.

A quick test using Apple's sample streams proves what you want to do is possible.

MPMoviePlayerController *player = [[MPMoviePlayerController alloc] initWithContentURL:[NSURL URLWithString:@"http://devimages.apple.com/iphone/samples/bipbop/gear4/prog_index.m3u8"]];
player.movieSourceType = MPMovieSourceTypeStreaming;
player.view.hidden = YES;
[self.view addSubview:player.view];
[player play];

I used the audio streamer by Matt Gallagher in one of my apps. It's an internet radio app pretty much like Pandora and LastFM. And yes it was accepted by Apple and has been in the App Store since then.

So in my opinion, your plan B is actually not that risky. :-)