I could totally get behind Vaughan directing Episode VII. I just don't see Disney/Lucasfilm wanting him.
He has a history for bailing on productions for various reasons, and they need to get Episode VII going yesterday.
He's also very strong headed and opinionated...which I think is great for an auteur, I'm not criticizing him. But I don't see Disney/Lucasfilm wanting someone who's gonna' fight them on major creative decisions. I see them going for a journeyman director, with a star writer.
I could be wrong, though...we'll see soon enough!