You know in the first Thor movie when Thor was stripped of his power and sent to Midgard as punishment? I had an idea where either Midgard turns out to be Nirn, or Akatosh borrows him. Whether at this point Thor finds himself waking up in a cart as the new Dragonborn (probably this if Akatosh borrows him and gives him a blessing) or as a bystander who gets to watch the female dragonborn get nearly killed and ends up companioning her around (probably this if Midgard is Nirn).
In either case, Thor has to learn what he does in the movie somehow, that is humility. Might be easier if he's not the Dragonborn in this case, wherein he can learn by example and perhaps a budding romance can start there after Thor kinda gets over himself and Miss Dovakiin starts to fall for the better Thor after he stops being a boor.
Either way, I figure best bet is that instead of the Notched Pickaxe at the top of the world, it's instead Thor's hammer. Whether he's worthy of it yet by the time he finds it (pretty sure Parthurnaax might bring up something about it, like Thor needing to go higher in some cryptic way) is entirely up to what state he's at. He might even need to go back later after he's learned his lesson.
I had a few side ideas to this as well, such as Alduin being one of Loki's children, and there's the whole story arc of what he's doing as well. How that will be changed by Thor ending up on Nirn could be interesting, especially if it's Akatosh borrowing him and him getting surprised by it. Either way, I don't think I'll be writing it out though since I don't think I could do the idea justice. So, this is up for adoption.