Yeah, she's always looked like she was wearing pajamas....
But some feedback on your design:
1) Her cuffs usually go further down and form a triangle or drape down (depending on the artist).
2) Also, many artists pull wrinkles or folds at elbow, waist, ankle, knee, etc to counteract the "pajama effect".
3) You could go "Dirty Dagger" by expanding the naked-cross motiff by adding slits to her leggings? Or a "dagger" design exposing her back and or ass mirroring the effect of her front design?
4) You could go more the "Marvel Ultimate Alliance" game route and give her more of a "street" look? (Personally, I think this is the best idea. Your Elizabeth corset could be a good starting point?)
5) You could go the "X-Men" Dagger route which added some details to her costume. Not my fave though. And wasn't around for long so probably not a lot of fans for this one.
Also, just found this site. Seems like a good resource for character refs.
http://charactermodel.tumblr.com/