I’m not so sure about McCain’s eligibility. I’ve seen it argued from early legal sources (can’t remember which ones) that the children of a nation’s ambassadors are natural born even if they are born on foreign soil while their parent is serving as ambassador in that foreign land.
I don’t know how the law classifies military folks, but I would consider them ambassadors of the US when serving abroad.
That issue is for the courts to decide. It frustrates me that the court can do all this penumbra mumbo-jumbo regarding stuff that’s not even in the Constitution, but a question that is directly from the Constitution won’t be addressed.
You can argue about anything. But a person born in another country under a foreign sovereign is not a natural born citizen for US Constitutional Law purposes no matter who his parents are or why he was there.