Gratuitous Skyrim/Dragonborn spoilers abound, if it needs to even be said.

I've always played with the idea that Miraak was originally the one Akatosh chose to bestow the gift of Dragonborn unto, so that Alduin could have been defeated then and there during the original Dragon Wars. But Miraak decided he'd rather get buddy-buddy with Herma-Mora, and so the only choice for the humans at the time was to send Alduin into the future with an Elder Scroll. And then the future came around, and Akatosh tried the whole "Dragonborn" thing again with you. You had one job, Miraak!

Hell, Miraak's return actually coincides with Alduin's; one could suppose that if the player character wasn't involved at all, Alduin and Miraak would eventually be forced to clash, seeing as how they have conflicting interests. Could the First Dragonborn have been the Last Dragonborn? And how do you suppose Miraak vs. Alduin would turn out?

Okay, maybe "Hero" isn't the best way to describe Miraak; if he has control of his own fate, could he really have been taken in by the Daedric Prince of Fate? On the flipside, it jives with his whole "only one who can defeat Alduin but chooses not to". Maybe Miraak is what happens when the player character puts off the Main Quest for a few Eras.

Interesting idea, though I have nothing to add to it unfortunately. It does make a certain amount of sense, although I don't know about the Dragonborn becoming nu-Miraak, but I guess someone's Dragonborn could have.