The Empire licks the boots of the Aldmeri Dominion. They even go so far as Outlawing thier patron god for these uppity high elves. That's inexcusable from an Empire forged from said God. The Empire in it's current state is just a puppet for The Aldmeri. A puppet that needs to be burned off the hand before being resitched.
I'm not normally big on lore, but I do find the tactics of war interesting, so I'm just going to throw this out there: the Empire is showing signs of recuperation-before-retaliation. Some times, to find the time for such a breather, you've got to give the opposition reason to relax. For the Empire, from what I've gathered, that was a treaty excommunicating one of their personal deities. That's one thing.
The other thing is, if Skyrim was to dishevel itself away from the Empire, it would not stand long. If a conglomerate body is incapable of fighting the opposition, a culturally-emancipated but politically-destitute one stands no chance whatsoever. As it stands, freeing the lands for the Nord is just freeing the lands for the Aldmeri. More than likely, there wouldn't even be a period for chance of surrender. As soon as the reigns of Skyrim fell lax in the hands of the Empire, the Aldmeri would trample the people and lands and retake reign for themselves. No question.
But, again, that's looking at it from a real-world perspective. This is a fantasy world which behaves completely at the writers' whims, so yeah. Have fun with your debate anyways. Ta-ta.
EDIT: Fixed some redundancy.