Zhao Wei = an excellent Mulan.
IMO, Zhang Ziyi, Michelle Yeoh or Liu Yifei would not fit the role at all, esp. Yeoh, who is waaaay too old for it. I think Yeoh's 46 or 47 now... a year or two older than me, anyway. Unless the movie's about Mulan in middle age.
In those old KF movies, I always thought it was a joke they couldn't tell a hottie from a man just because she put on men's clothes and tucked her hair in a fedora. Her voice and face would still be the same; she'd even still have makeup on! But then again, if Americans couldn't tell Clark Kent was Superman because of the suit and glasses...