http://m.ign.com/articles/2017/03/21/original-ghost-in-the-shell-director-mamoru-oshii-has-no-problem-with-live-action-remake
"What issue could there possibly be with casting her?" Oshii told IGN by e-mail. "The Major is a cyborg and her physical form is an entirely assumed one. The name 'Motoko Kusanagi' and her current body are not her original name and body, so there is no basis for saying that an Asian actress must portray her. Even if her original body (presuming such a thing existed) were a Japanese one, that would still apply."
"In the movies, John Wayne can play Genghis Khan, and Omar Sharif, an Arab, can play Doctor Zhivago, a Slav. It's all just cinematic conventions," he explained. "If that's not allowed, then Darth Vader probably shouldn’t speak English, either. I believe having Scarlett play Motoko was the best possible casting for this movie. I can only sense a political motive from the people opposing it, and I believe artistic expression must be free from politics."