Natural born means born to natural whole allegiance.
There always will be cases not fitting well, but keep the simple principle in mind and cases are then honestly decided. It is the Principle that is the foundation upon which laws and rulings are built -- it is a persistent trouble to Law and Justice that otherwise wise people want to pour the concrete in the wrong place -- and set concrete detailed standards that apply in all circumstances -- and by so doing obscure and bury the Principle with statute and case law so much so that the applied law becomes at a total perverted odds with the Original.
The foundation is all Principle. Affix your arguments and reasoning to that solid foundation.
How does one go about measuring the "natural whole allegiance" of a newborn in any objective manner? It's such an objective standard as to be meaningless. It gives us no guidance whatsoever and could be used for any political purpose.
The foundation is all Principle. Affix your arguments and reasoning to that solid foundation.
Your proposed foundation is built on shifting sand.