I disagree with all of this and with your statement that Sansa's "trope is the princess in the tower who wanted to marry a handsome prince and be a lady in a song/fairy tale." I think that's too incomplete a description to constitute a real trope. Her trope is more that of the beautiful, initially shallow princess who eventually realizes that good looks do not always mean good character, and vice versa. So it makes more sense for her to end up with someone whom she had misjudged at first, such as Tyrion or the Hound. But I also think that that trope could be deconstructed to some extent if she actually ends up single, realizing that she doesn't need a prince (handsome or not) in the first place. And on a side note, it would be even more of a deconstruction if Arya, the tomboyish princess who never thought of getting married, is the one who ends up in a romantic relationship, while Sansa chooses to be on her own.