I just don't see how this fits with your previous statement that "a law which grants citizenship is, in and of itself, an act of naturalizing a group of citizens." The way I see it, this would create a sort of Catch-22 problem where the very act of redefining "natural born citizen" makes those people it includes not natural born citizens.
"a statutory law which grants citizenship is, in and of itself, an act of naturalizing a group of citizens."
There's a significant difference between Congress passing naturalization laws and Congress amending the Constitution.