After finishing the civil war questline for either the stormcloaks or the empire... wouldn't it be cool to actually become a jarl yourself. Maybe a continuance of the civil war questline where you help Ulfric become High king by convincing the other Jarls to choose him at the moot.
As a reward Ulfric proclaims you Jarl of some smaller hold... like for example Roriksted. Then there could be an entire questline to bulid up Roriksted and a great money sink for high level characters. Build a fortified house (smal castle), get merchants and the like to settle there... maybe even gather all your houscarls (and make them thanes), which you got by becoming thane for other jarls, at the same spot. Do quest to convince the brotherhood, the thieves guild and even the college of winterhold to establish brances in your hold.
And a main questline about defending your borders against the forsworn and at the same time keep the peace with bordering jarls.
Oh... and your spouse if you got one could become your steward and instead of giving you only cash from his/her store he could also be the one collecting the hold tithe... crops from the farmers, ingots from the blacksmith etc etc.
I'm actually suspecting that Bethesda got some sort of continuance for the entire civil war planned already... since Ulfric as of yet hasn't become high king... but im not sure this continuance would include the dragonborn actually becoming jarl himself. Which i personally think would be really cool.