Interesting how when you look back in history at how many items of clothing that are now called woman's wear was once considered men's fashion. Skirts, hosiery (tights) , high heels, one piece swimsuits, leotards, makeup are a few examples. While the swimsuits might not of been what you see today. But then it was against the law for Men to bare their chests. So they had to wear these one piece swimsuits. This was in the early 1900's. Men switched to pants basically to ride horses into battle during a war and because a French king got defeated by a pants wearing army. That's essentially the only reason why Men stopped wearing skirts and tunics. Then some other clothes became socially unacceptable during the Queen Victoria era, or the prudish era. And that's when clothes became gendered and to wear clothes of the other gender became socially/morally unacceptable and laws made. Otherwise there is no other reason for gendered clothes. Granted some clothes have to be a bit different to allow for different body features (breasts and hips) of men and women.
Today the only roadblock is really the social and "moral" aspect of wearing the opposite gender clothing. We don't ride horse into battles anymore, we don't have a Queen Victoria dictating fashion. There's really no reason why men and women can't wear the same clothes anymore like they used to throughout history.
Trevor