” A baby born to an American mom is eligible.”
Not if he is born in a foreign sovereignty to a foreign national father. The only thing his American mom made him eligible for is the Senate or House of Representatives as a Citizen. For Article 2 Section 1, it takes more than a Citizen, it takes a natural born Citizen.
The Presidential line of succession includes Speaker of the House. Surely they’d have to conform to your definition of NBC as well, right?