Sam Mendes just popped in my head. He directed American Beauty and Road to Perdition. However I'd like to see him tackle a period piece sort of Superman, like It's Superman or the Max Fleischer cartoons.
He's soon doing an adaptation of Preacher. Don't forget that The Road to Perdition was also a comic adaptation, so perhaps he's something of a comics fan.
I haven't read Its Superman. Intriguing suggestion re The Coens. I'm a big fan of theirs, but I'd be surprised if WB handed over such a tentpole type movie to the hands of such offbeat indie darlings, even allowing for their recent mainstream successes. I'd love to see a Coens-cast Superman, though. Malkovich as Luthor? Josh Brolin as Supes? Jeff Bridges as Perry White ('Clark, I love you, but you've got to face the fact that you're a goddamned moron!')? John Goodman as Doomsday?!