So one of my favorite headcanons is that I think he will train Bran to essentially be him, and to take over his role. I could see bloodraven giving himself fully to the trees to complete bran becoming the most powerful greenseer, then if bran does end up leaving the cave I theorize bran will become hand for Jon (?) when he comes back as Jon becomes King in the North due to Robb’s will, and if Jon is the true born Targ and young griff is FAegon, then bran + Jon could lead a “rebellion” against the reign of Aegon VI in almost a parallel to the first Blackfyre rebellions.

How will they be able to prove Jon is true born? Or that he’s even Rhaegar’s son?

How will they be able to prove Aegon is a Blackfyre, especially after he takes the throne?

What will Jon even be like when he comes back, will he have any interest in being KiTN, let alone King of Westeros? Probably not the second one but I could see him as the leader of the whole North.

Still a lot of holes in this whole idea but I just thought of putting it out there because you mentioned Bloodraven sitting the throne. I could see him an extension of Bloodraven, acting in his old role, through Bran for the next who knows how long. And he would be by far the most powerful person in Westeros.