I think it's a great idea.
A large part of the argument for wearing uniform is about the fact it's a great leveller and instead of pupils being defined by their own clothes, financial means, fashion sense, etc, they are all on a level playing field.
I believe that having different uniform for girls and boys sends the subconscious message that it's necessary for some reason and implies that there are fundamental differences between men and women that require them to wear different clothes. This, in turn, feeds into the notion that some academic subjects/careers are for women and others for men.
Eliminating the difference in uniforms will hopefully start to eliminate some of the institutional sexism that seeks to hold our girls back.