> Peggy tells the story of marrying Alex Campbell herself, in The Peggy Seeger songbook. So it's pretty much gospel.

Yep. I've always thought that Cyril Tawney's song New Names For Old was about this, though it also introduces some emotional vulnerability into the mix. I have no idea whether that aspect is true or not, but it certainly makes for a poignant song. A Cyril-related webpage (not his official site) asks a similar question:

NEW NAMES FOR OLD (1968)
If a career-conscious American lady offers a fellow money to give her his name and British nationality in a marriage of convenience, with no strings attached, he might well turn her down, as a friend of mine did. But what if she's the girl of his dreams? Might he not take a chance on something more permanent?