This really makes me think about how Kripke had Misha audition as a demon before revealing the truth behind the role. How would Castiel be had he actually been a badass demon who mysteriously brought Dean back from Hell? How would Misha had played him, the same? Or entirely different? And what reason would his intentions be?

Yeah, I think about this kind of stuff. But it's an interesting concept to think about. Either way, Cas was created to be a BAMF. ;)