Any person who was a citizen, at the very moment of birth, is a Natural Born Citizen.
This simply means that no “naturalization” process will work to grant eligibility for POTUS.
This simply means that no legal action or legislation or any other attempt at “retroactive” citizenship will work.
If I were an argumentative soul, I'd say something to the effect of..."But you aren't John Jay and it wasn't your idea to include the phrase in the Constitution. Aren't you just a little curious what it meant to him at the time he inserted in the the Constitutional draft?"
But, I'm not an argumentative soul, at least not in my retirement. I grant you your understanding of "Natural Born Citizen", and admit that your position is completely defensible. If I had a paying client, I'm confident I could argue both positions with equal effectiveness. Usually, it's just these kinds of controversies that the Supreme Court loves to wade into. But, for whatever reason, this court (and all prior courts) hasn't the appetite to consider such a complex and confusing Constitutional puzzle.
The best analysis I've read was a written by a University of Illinois Law School professor as a commentary that appeared in the University of Michigan Law Review. Interestingly enough, it was written to address the concerns of some about John McCain's presidential eligibility, not Obama's. The author is a well-received and widely recognized expert on the varying kinds of constitutional originalism, with specific emphasis on semantic originalism, which is incredibly germane to the topic of "natural born" citizen.
Again, while he attempts to dissect McCain's eligibility dilemma, much of what he writes encompasses Obama's possible dilemma as well. I don't know your level of legal understanding or knowledge, and the document is rather wonkish and professorial (as one might expect from an expert law professor), but IHMO, it's worth the read if you've got :20 minutes.