Falci: Ghost in the Shell is a series with a funny thing for its protagonist. Every new interaction changes something about Motoko. The original manga had her being very feminine and sexy, bissexual and foul mouthed; the movie anime had her being very androginous, muscular, contemplative and not even being phisically unique; SAC had her a bit closer to the manga incarnation (though I find her uniform in this highly inapropriate, probably because I'm already old); Arise had her younger and shorter.
And now the fuss is all about her being western, when the series lore can easely fit her brain inside whatever body she wants.
Personally, I think Scarlett will do fine, particularly if they're going for a anime-movie like Motoko, in the sense of being more introspective and contemplative.
Though, I got to admit, Kusanagi's hair style doesn't fit her very well.
GitS is one of the few franchise where the anime is way better than the manga.