I have no problem being the first to say it's sexist. That skin is not about creating a different sex character skin: it's about boobs. The character skins are supposed to be indicative of the archetype they embody, and the male ones are great and funny because they do just that. I'd hope that female versions could be less about gender roles in gaming and more about creating the characters. And no, the female pyro doesn't go nearly topless as a character trait.
Rant over, I love you all.