Well...it's not a new theory.
But I think you're looking to hard to fit things plot-wise when actually, they're just thematic parallels because history is cyclical.
Like the Night's King is just a mini-sequel to the Bloodstone Emperor of the Great Empire of the Dawn. They're basically the same story set on different continents at different time periods.
And AA is a messianic figure like the Last Hero. And AA may have been several different people.
And Lightbringer may not have even been a sword but a person or a dragon.
This stuff will get expanded on in the GOT prequel though and GRRM already said that the history we think we know may not even be true so the canonical status of all this may be thrown into the trash so the prequel can have a fresher state.
Well you're not working from more information than I have to come to those conclusions, but mine actually relate to what's written, no offense:p
The Last Hero was looking for the CoTF with his 12 companions.
The Others close in on him, everyone else died, even his dog, his sword snapped from the cold.
????
The Last Hero has a sword that the Others can't withstand and he beats them.
Clearly, his broken sword would be no good against the Others, so he somehow obtains a sword no one had before to beat the Others. How? Sam says he supposedly had a Dragonsteel sword, and Jon wonders if Dragonsteel is Valyrian. The Children of the forest do not forge steel.
It seems there is zero reason to believe the Last Hero met the CotF, so how did he come out of this alive, and then somehow get an awesome sword to beat the Others?
Then, we have Old Nan who says the 13th lord command (12 companions + 1 = 13th) was the Night's King, and that he was "man by the light of day, but the night was his to rule", and that maybe his name was Brandon. If he is man by day, but NK by night, then the character would likely be in conflict with himself.
Where did the Night's King find the Corpse Bride? The Haunted Forest. Where was the Last Hero when he was "dying"?
Azor Ahai is seemingly really bent on forging an awesome sword, but we don't know why. Day-time 13th lord commander/Last Hero would have a pretty good reason: the sword he had was ineffective against the Others, he needs a better weapon, and why make a new sword that will break again against them? I don't have clues indicating that Coldhands stabbed himself in the heart with a dagger, but the show has a book with a page about dragonglass used as a
cure, and since they sort of merged Benjen with Coldhands it's pretty likely it makes sense. The CotF say Coldhands died long ago, so he came back to life. Flaming heart, frozen fire, dragonglass in the heart, Azor Ahai's wife stabbed in the heart with Valyrian steel/Dragonglass?
This is an illustration for Brandon the Breaker killing the Night's Queen. Or is it Azor Ahai stabbing Nissa Nissa?
What did the Corpse Bride look like? "Skin as white as the moon, eyes like blue stars"
It says the face of the
moon cracked due to Nissa Nissa's
cry of anguish and ecstasy when
Azor Ahai drove Lightbringer into her. Tears rolling down the face of the Corpse Bride? The "white" corpse bride no longer being "white", as in, the moon cracks because she is turned back from being a moon-white-skinned Other?
So Brandon the Breaker, breaks the curse over himself, kills or frees her, forging Light Bringer, and defeats the Others with Joramun.
Seems like a really strong case.
Also, wouldn't surprise me that GRRM made it that the Western myths are the original ones, the Eastern ones the derivative ones. A switch on our world.
