The reason for this is that the characters aren’t Japanese, despite the actors playing them are, saying that this was “a bad idea”.
Granted, the movie industry is plagued by accusations of whitewashing, but we rarely see it go the other way around.
The statement was dropped by anime director Seiji Mizushima, speaking at a recent stage show in Tokyo, saying, “It was a bad idea to only use Japanese actors.” he also added that “If you asked me whether I think the cast could pull it off, I’d say that no, they can’t.” and said “It’s hard for actors to capture the look and feel of the original manga.”
Despite all this, he doesn’t hope that the live-action FMA movie will tank, but is, in fact, rooting for it despite the bad ideas.
As for us, hopefully we’ll get to watch it too when it comes out in December this year when it launches.