i had this thought in the shower this morning that sansa choosing tyrion after everything that happened is the only thing that makes sense to me.
she would realize that unless she has an heir, as she gets older her position on the throne at winterfell might be threatened and/or after her death might cause chaos as people (men) fight over her replacement.
bran/the three eyed raven doesn't seem like he/they would choose to marry/reproduce.
tyrion, as bran's hand, makes sense politically. that would help solidify the alliance between the queen of the north and the king of the seven six kingdoms.
tyrion is, presumably, still heir to casterly rock. if sansa and tyrion have multiple children, one of them would inherit the north and one would inherit casterly rock.
but most importantly, sansa told tyrion he was "the best of them," and it wouldn't work because of his loyalty to daenerys. well... she's gone now, and he's loyal to her brother, her ally. but more importantly she knows that he isn't uncomfortable with having a woman ruling and following her orders.
and if it stayed purely as a political/convenience marriage arrangement, i think sansa (and maybe tyrion, because he might be afraid of them turning out like his shitty family if he was more involved) would be okay with raising their children in winterfell with a yearly visit from tyrion.
i think all it might take to kick this off is for tyrion to send an official raven to sansa with government business stuff, but sign it something like, "love forever, your favorite husband tyrion."
