Can you explain the Watsonian rationale behind Sansa marrying Ramsey? Giving Jeyne/Arya worked because the Lannisters weren’t REALLY giving the Boltons a useful marital asset; they couldn’t gain anything by offering Jeyne elsewhere, but LF COULD have used Sansa’s hand for all sorts of other deals. The Boltons bring nothing but the North, to which Sansa has a better claim. Also, this marriage could COST the Boltons their southern support. Is the legitimacy from a Stark bride worth that? Continued
I don’t think there is a good one; LF’s idea of rallying the Vale behind rescuing Sansa is pretty implausible IMO. Honestly, this was an area where the show’s writing didn’t so much decline as start at the bottom and dig itself deeper.
But yes, it is in the Boltons’ interests, because Roose pretty much discounts the southern support as being worth anything once he’s past the Neck.