Sorry, but I have to disagree with you on this one. I believe the Framers intended that BOTH parents be born here. That is what separates natural born from being born to naturalized citizens. You know your Old Testament. The concept is directly taken from the Hebrew Exodus.
Not that I disagree with your concept of NBC. I rather like the idea of NBC extending back two generations, which would be an even stronger deterrent to foreign interlopers and usurpers of the office of President.
However, I don't believe that Vattel's description of NBC extends beyond one generation (that of the person in question).
The parents had to be citizens, either naturalized or native.