Mulan is in a bit of an odd position from Disney marketing's point of view. She's no a literal princess at either the beginning or the end of the film. She spends more time disguised as a man than she does wearing a pretty dress, which Disney tends to push as a big selling point of their princess merchandise. She battle marauding Huns instead of going to the ball. The first scenes of the movie are largely devoted to showing that she's
not very good at doing proper girly things.
Still, I do wish Disney would do more with her and some of the other non-princess Disney ladies. It's perfectly fine that some girls love the standard princesses and their beautiful dresses and their particular stories, but not every girl is into that and I can't see why Disney wouldn't want to promote role models for all kinds of little girls if they can make a buck in the process. Among others, I'd love to see more attention paid to Jane from "Tarzan" who does actually wear a pretty dress through roughly half her scenes in the movie (though DH finds her later outfits much hotter.

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Aside from that, it would be nice to see a little more diversity in the "princess" lineup. Jasmine is generically Middle Eastern, but all the other current princesses are Caucasian. Again, I can't see why Disney wouldn't want to push characters like Mulan and
Pocahontas (who, as the daughter of a chieftain, is an actual princess) in their Princess lines, if only so more little girls can have a princess who looks like them. I'm hoping the release of "The Princess and the Frog" will aid Disney in figuring this out, but who knows?