Yeah, this is definitely different... It might explain why Miranda looks pretty unhappy in that short clip... if Ramsay is being married to someone else she isn't going to be very happy. Hell, they hunted down that girl last season and fed her to the dogs because she made Miranda jealous.
I think it's more likely that the "marriage" is a ruse to get Sansa close enough to get revenge on the Boltons. I think LF wants her because she reminds him of Catelyn... and what better way to get her on your side than to allow her to get revenge on the people who betrayed her brother/mother? Not to mention that LF himself probably wants to see them dead for killing Cat.
The more I talk about it, the more I'm convinced that is what is going to happen. LF gets Sansa a chance at revenge, and possibly reclaiming Winterfell... knowing the North will rally behind a Stark...
If you think about it, this is another way of getting to what he talks about in the book... marrying her off to... Harry the heir was it? Don't remember... but he talked about "her" getting Winterfell back and such (and asked for a kiss in return). Yes, this is eliminating a few characters from the North and the Vale stories, but ultimately would head towards the same end... control of the Vale and the North.
If I'm on the right track here, these are the kind of changes that would streamline the story for the show and still hit the end goal... probably in a more satisfying manner than what will happen in the books. Sansa/LF being the ones to get the revenge on the Boltons would be a bigger emotional win than Manderly and co... and we don't need to bring in a bunch of characters no one remembers or cares about.