Some are the main characters like Kasumi and Helena, but Hayate is too. Ayane, Christie, and Hayabusa appear a lot.La Mariposa and Kokoro are getting some more attention to the story. The rest have their own motive that doesn't connect to the whole corporation(Tina wants to be everything, Lei-Fang wants to defeat Jann Lee, and I think Hitomi wants to look for Ein, which of course, is Hayate.)
Overall in the game they focus more on the Ninjas. They center it around Ayane-Kasumi-Hayate relationship, with Hayabusa turning around them. Other character like Helena or Christie have there story wich cross a little bit with them but not that much. In the guys honestly exept from the 2 ninja the other guys really are not much important. I mean they have there story but thats all, they dosen't link much to the main DOATEC-Donovan story.
And as for Tina, she have her cheesy story with Bass, but she is really outside the main story. I guess they make her a main character in the movie cause she is a fan-favorite for her blonde-bimbo-with-big-boobs look.
But the biggest and funniest thing is how Christie is a main character when she is far from it in the game, and very different too.