My son was born in Landstuhl Germany at the 2nd Army General Hospital in 1978 - I was a citizen and an Air Force Officer at Ramstein AB and my wife was/is a citizen - and it was not as clear cut as you make it sound. Both military and State Department personnel briefing the new parents said that if any of the children aspired to be President, then it would have to be determined whether or not they qualified as natural born. He was issued a "Certificate of Birth of an American Born Abroad", but that doesn't say natural born anywhere on it.
In essence, 3 words: to - be - determined...
Never has there been an issue that two married Americans, one on military orders with dependents, would ever have their child not be a US citizen. “Natural born” is not a tricky definition by any means. Any child who is a citizen under US law at the time of birth is a natural born citizen.