Popular Artists Dubbing Actors in Movie Musicals

I'm watching Sia perform on SNL and her particular style of performance has me wondering if we could ever see the day where artists from popular music are tapped to record the vocal tracks for actors to lip sync to in movie musicals. It would be an added marketing point. I just kind of wondered why a musical had never tried getting a big actress and a big pop star. I'm not sure if it's something I'd really like to see happen. I like my actors to sing but there's some situations I might see myself getting on board. Next to Normal comes to mind.

I think this is a great idea. Film should always be about illusion. If you can create a perfect character with the singing voice of a singing star and the acting/looks of an actor, why not?

People have shared roles before (Jasmine in Aladdin), and both performers can get praise for their part. Also in the old films and more recent films (Phantom, Carlotta), but I think sometimes ego's get in the way.

For me it's all about the quality, so I would rather have the best singer dubbing, known or not. But it seems that producers look for names instead of talent, so this could be a solution.