Seriously, if you do the season unending quest if Ulfric will try extremely hard to gain back Markarth and is willing to hand over Riften to the Imperial Legion. This is not strategically sound because if Markarth is under Stormcloak control, they will still be surrounded by Imperial forces with the surrounding provinces controlled by the Legion and High Rock controlled by the Legion, allowing the Imperials to have Riften would just give the Legion a foothold in the Stormcloak dominated eastern provinces of Skyrim.
Any thoughts?
There's a more basic point.
The Romans, Sun Tzu, Von Clausewitz, Phillip II of Macedon, all the great military minds in history knew one principle extremely well:
The only time you meet your enemy on the field of battle is when you've already won.
Ulfriq should have spent more time politicking. Challenging the Solitude High King was a smart move. Having taken back Markarth from the Forsworn gave him additional 'street cred.' Instead of breaking so overtly from the empire, the smart thing to do would have been to marry one of the emperor's niece's to cement an alliance, work up a scheme to keep the Thalmor distracted and tied down with trying to eliminate Talos worship in Skyrim (perhaps focusing on Markarth, so that the Thalmor are more likely to run into problems with the Forsworn and the Falmer as well, combined with the inherent difficulties of that very rocky and steep terrain), win the allegiance of all the Jarls by professing to be in favor of Skyrim 'autonomy' while still maintaining allegiance to the empire (a deception, of course), and build up Skyrim thru eliminating bandits and the remainder of the Forsworn (perhaps in a false allegiance - "We'll give you back Markarth if you help drive the Thalmor from Skyrim").
In the end, with Skyrim strengthened and united, the Empire given time to recover, and the Thalmor off balance, overstretched and confused in the Reach, it would have been a simple matter to convince the Emperor to let Skyrim declare independence, as it would be too difficult for the emperor to resist such a request. A sweetener could be an agreement to draw the Thalmor into a precipitous attack on Skyrim (either thru an escalation of their involvement in the Reach or more generally), using the western mountains to channel their attacks to their disadvantage and giving the Empire's forces freedom of maneuver for a counterstrike.
I need to develop an Expansion.