Re: "All of the versions considered together suggest the story of a love affair between a travelling enemy soldier and a local girl which is thwarted by the girl's ambitious mother who wants a son-in-law with more money and a higher social status."

Somebody is being naive. The song is about an officer (Captain) who wants to seduce a girl of the lower classes and will probably dump her among the camp followers once he's lost interest. The girl is too smart for him.

Have you heard the line, "In coaches you shall ride, with your true love by your side, just as grand as any lady in the areo?" It shows that she is not a lady, she's a servant or farmer's daughter, something like that.

She's afraid to reject him in a straightforward way, so she calls on her mother's authority.

The captain doesn't really die of love in Louisiana, (pronounced Loo-zee-anna; he dies of one of the many diseases that swept military encampments. When you do the song, allow a musical interlude after the threatening verse so that the singer (the lower-ranked soldier) has time to figure this out. Then sing the first again, tenderly, as is he is remembering the captain and what a rascal he was.