for thor, i'd probably go with karl urban.
Captain America: Ben Browder
Thor: Josh Holloway
Ant-Man: Bill Campbell
The Wasp: Grace Park
Ant Man: I like Hugh Laurie. Brad Pitt could also do twisted and disturbed doctor.
Hawkeye: if really in the movie... maybe Paul Walker or Colin Farrell
Iron Man: Downey Jr. of course
Wasp: Claire Forlani maybe
Black Widow: Angelina Jolie
I'm not quite content with my list. first of all, there sure are better picks for the latter half and second. too many stars.