Nonsense. McCain is NOT president, so an example, he means nothing.
If children born of US citizens serving in the armed forces overseas fall into some limbo in your system then your proposed system is idiotic.
It's not a matter of limbo, but of having a court citation to follow. We have court citations that recognized all children born IN THE COUNTRY of citizen parents as natural-born citizens. We do NOT have a citation that affirms Vattel 217 regarding children born out of the country in the armies of the state.