The easy answer is that Kitty has been portrayed as the young teen X-Men girl for so long, that the transition to irresistible sexpot is a bit of stretch, but there's no reason not to portray her as tough and sexy now - which is what I try to do.
Yeah, it's kind of hit and miss. I know that Wheedon and Cassady did some things to advance and mature the character, but like always those changes go away with the creative team that created them. My hypothetical question was more commentary on how changes are made and dashed upon the rocks as quickly as it takes to close the cover on the issue you're reading.
I like how you portray her, strong and sexy. IMO she's the star of this cover, not Emma.