I think the live-action series should be based on the manga, because the anime wasn't even though it was still a masterpiece. As for the other stuff:
Will it be westernized for an english speaking audience?
I think it's better if the movie had the same setting and outlook as in the anime, to not lose its originality
Will they cast the characters wrong?
Let's make sure they don't get Hollywood actors in this movie, otherwise it's gonna be SHIT...
Will the soundtrack be written by yoko kanno like the original?
I doubt this, although it would be good to have the original OP/ED get pimped up