I really don't care who plays major but I don't want Rinko acting the role. Only movie of hers I watched was Pacific rim and I found her acting appalling (but her character which was equally bad to say the least helped me lot to dislike her acting). If I would go for a Asian actress i would go for Eihi Shiina. Watched more movies with her, ahd at least the same acting skill. Looks much more imposing and threatening, and action B movie shlock is her kind of thing so, hell yea.
BTW, there are Asian looking characters in Ghost in the shell. But Section 9 team was purposely drawn NOT to look Asian. If I remember correctly, Makoto's body was modeled more after Caucasian type body because It's military hardware and being Caucasian has best psychological effect on the field on both opponents and friendlies.
As for nationalities I envisioned...
Makoto Kusanagi, The Major - none, she is a concept of humanity in my mind. Caucasian body.
Batou - USA/Canada?
Ishikawa - USS of R
Saito - East Asian, 100%
Paz - South east Asian of southern South American. Maybe even Spanish/Portugalian.
Bouma - stereotypical Japanese, so, Japanese, maybe Mongolian with withdrawn personality
Togusa - I think his official story is that he is half Japanese, half Caucasian, couldn't agree more
And that's How I would like to see them in the movie too. So, Scarlet is OK,