Humans in general are designed to effectively reproduce, but I actually don't agree with this at all.
1. Women are weaker because, since they bare and raise children, they were far less frequently hunters than men. We thus did not evolve to be as strong or tall as men are -- Amazon women are a different case, and similarly tended to be tall and strong.
2. Neither can men, without psychologically controlling it, which is also possible for women (you start getting horny, start thinking about things that worry you or upset you, it will most likely stop), and humans aren't designed to do anyway
3. That's just false. Every rape victim here I've ever read about has testified to the fact that it is not possible to achieve orgasm during real rape. (Of course, the vagina will still produce lubricant to protect itself against damage, but that isn't cum.)
4. Your parenthetical is complete opinion, the vagina is only hidden because of social stigma (which has nothing to do with the biological approach you're taking -- nor does humiliation), and I would argue that no, the vagina is not completely exposed in said position if one's legs are closed. And if your legs are open, the vagina would not be hidden regardless.
So, no.
Hot idea, though.
