Which is why Skyrim needed a Third Option like you had with Yes Man in New Vegas. Seriously, you fucking kill Satan. Even before then, its all but spelled right the hell out that you'll kill the bastard dragon. Everyone knows it, but they seriously expect us to think that only the Stormcloaks or the Thalmor could start an army? The Dragonborn, by the time Alduin croaks, has enough money to fund a private guerrilla army. Fuck, the Dragonborn is an army all unto himself. Neither side would stand a chance against him, considering he likely has the ability to go invisible at a whim, and can incinerate an entire platoon by saying a couple of words.
Yet, the Dragonborn is doomed to be a mere follower, a pawn. No, fuck that, I'm the leader, and people either get the fuck with the program, get the hell out of my way, or kiss their arses goodbye.