I was imagining Sophia marrying a rather elderly Lord Brinklow for the sake of his wealth and title who conveniently dies shortly after she becomes pregnant with their first (and only) child, from whom Miss Wraxton is descended. I assume that her Ravenclaw characteristics are inherited from her mother.

Yes, I suppose that's true. He does defy his mother at one point as well, doesn't he? Unsubtlety is certainly a defining characteristics of Gryffindors, which is one reason I like them so much.