The other intriguing thing is, Kenneth Branagh most often acts in his directorial efforts; either leading or co-starring.
What role would he take in the Thor mythos?
Thor is out of the question.
Could he play Odin in heavy makeup, and being scaled for size?
Or...could it be Loki? He did a good Iago in the last version of Othello; that was quite a scheming character.