Do you only follow one line - mistranslated- out of Vattel?
Or do you actually follow what Vattel wrote?
Vattel:
§ 217. Children born in the armies of the state.
For the same reasons also, children born out of the country, in the armies of the state, or in the house of its minister at a foreign court, are reputed born in the country; for a citizen who is absent with his family, on the service of the state, but still dependent on it, and subject to its jurisdiction, cannot be considered as having quitted its territory.
If Vattel is accepted as the source of the Natural born citizen requirement, one might argue that Macain is a NBC.