Yeah, I agree with casting if the story is ingrained in a certain culture, like if there were a story where that Nazis recruited Victor Frankenstein to make soldiers for them, of course the monster would be a blue-eyed, blonde haired white guy, but if they're aliens or something, it doesn't matter what ethnicity the actor playing the guy is (one of the reasons I didn't get too worked up about Goku being white in the live-action dragon ball film was because Goku doesn't belong to any earth ethnicity. Not to say I'm not up for, let's say, a Native American Superman in film one day, but still).
Anyway, to bring this thread back to Ant Man, am I the only one dying for a cameo from Simon Peg, maybe as Hank Pym so he can pass the mantle to Paul Rudd's Scott Lang? Come to think of it, if it is Hank Pym who's the star of the film, will they incorporate his other alter egos? In the comics, Hank's been known as Ant-Man, Giant-Man, Goliath, Yellow Jacket. I'm hoping that they do like the recent Avengers cartoon and allow Hank to have access to both his Ant-Man and Giant-Man powers to switch back and forth and avoid confusion.