Since Congress can only enact legislation pertaining to naturalization, per Article 1, Section 8, Clause 4 (To establish an uniform Rule of Naturalization...), how could Congress pass legislation concerning a natural born citizen and then alter that legislation later, as you state, when it was never empowered to do so?
Aren't those "altered requirements" you're talking about merely changes to legislation previously enacted by Congress?
Congress DOES have the authority, through Legislation, to alter or change citizenship rules for Natural Born as well as Naturalized Citizens.
James Madison, Father of the Constitution, clearly said so, and I have posted his statement to this thread at least twice, already.
Since Citizenship rules were vague, at best, it was necessary for Congress to define the rules for Naturalization as well as for Natural Born Citizens.
The primary author of the Constitution, James Madison, said that Congress had such power.
That is good enough for me.