Well the Naturalization Act of 1790 said that "...children of citizens of the United States, that may be born across the sea, or outside the limits of the United States, shall be considered as natural born citizens." Is that defining natural-born citizen? Or is that just identifying those people as natural-born citizens?
If you understood what the founders meant when they referred to "natural law", you would know that making a law regarding "natural born citizen" is a contradiction in terms.
Except that the founders are dead, they didn't include their definition of natural-born citizen in the Constitution, so all we have is your opinion on what they meant.
Patent applications mailed to the Patent Office are considered as received in the Patent Office the instant they are delivered to the Post Office as Express Mail. The application isn't actually in the patent office, but as a matter of legal definition, they are considered as if they are. 37 CFR 1.6
For purposes of some laws, persons are considered children until they reach the age of 26. Under US Tax code, some exchanges (e.g., barter) are considered as money received.
I view the Naturalization Act of 1790 as a clear statement as far as the drafters of the legislation were concerned, that children of citizens of the United States, that may be born across the sea, or outside the limits of the United States are NOT natural born citizens, but "we will consider them as if they are."
By your standard, a statute that said "Persons born of British royalty shall be considered as natural born citizens" is not unconstitutional, because the constitution give Congress the power to define who needs to be naturalized, and it declared that persons born of British royalty do not need to be naturalized. Therefore, since they do not need to be naturalized (a power of Congress) they are natural born citizens. There can be no other possibility.