Admirable Privy

He already has to some extent. The characters act older than they are and there are funny bits like Jon Snow reminiscing about back when he was fifteen years old (the previous book, aren't you sixteen, kiddo?)

Maybe, but would Jon accept? I think Jon is serious about ending the thousands of years of war between the Northmen on this and that side of the Wall, and if Alys and Sigorn's marriage is any judge, I think he would prefer to pair up as many "feudal-ish" wildling chiefs like Redbeard, Tormund, etc with nobility south of the Wall as he can, including taking one to wife himself (assuming the NW oath is thrown out). He doesn't need to marry a Manderly to gain his troops, since they're both on Team Rickon at the end of the day.

Based on Pycelle's over the top denial in the Aerys II section in TWOIAF, it seems pretty reasonable to conclude that Aerys and Joanna were fucking before and after Joanna's marriage to Tywin, and that would absolutely drive a guy like Tywin crazy. Personally I think she died of natural causes and I don't like Tyrion Targaryen theory because it undermines Tyrion as a character, but the knowledge that he was second place in her heart driving Tywin to kill his wife is plausible to me, and witnessing the birth of a deformed child that "must be" a Targaryen mutant stillbirth like the many of Rhaella's that Tywin may have witnessed being the trigger seems plausible too.

Here's some wild tinfoil: Stoneheart might willingly pass on her flame of life. Has anyone seen Ned's remains? AFAIK all we know is that they haven't made it past the Neck into the Barrowlands, and Stoneheart is currently operating in the Neck.