Well Hulk is amazingly strong in TIH, so why not Thor? As for the alien aspect I have to say that I really hope and pray that they do not go that route. I think that the Asgardian gods could be handled quite well if they treat Thor's interaction with the other Avengers somewhat like they did in The Ultimates. Please don't flame me, I know that Ult. Thor was horrid in SO many ways, but I actually liked how the rest of the team thought he might be delusional about being a "God". Only Thor (and the audience) would know the events in Asgard leading up to his banishment to Earth. The others can all debate that he might be an alien due to his incredible powers, but since the main villain will obviously be Loki, than maybe in his defeat the truth of Thor's lineage will become clear to all.