My friend, NO ONE WAS ELIGIBLE. Forget about the founders, NO ONE WAS ELIGIBLE for POTUS with out the grandfather clause because the United States didn’t EXIST until the constitution was ratified. The Colonies became States, and the specific sovereignty they had before that ceased to exist.
The grandfather clause was there because no one was a citizen or had parents born there until it happened. It had nothing to do with the founders specifically. Sheesh. Maybe you should read something like Roberts Rules, or some other Parliamentary guide.
OK, so without the grandfather clause, no one was eligible because the United States didn’t exist prior to ratification, so no one could have been a “natural born citizen” of the United States. Agreed.
The point is, that would have been true, regardless of whether “natural born citizen” depends on birthplace, parentage, or both. If birthplace determines “natural born citizen” status, then no one could have been a “natural born citizen,” because no one had been born in the United States 35+ years prior. If parentage determines “natural born citiszen” status, then no one could have been a “natural born citizen,” because no one could have been born to United States citizen parents 35+ years prior. So, trying to argue that the existence of a grandfather clause proves that “natural born citizen” status depends on parentage is incorrect.