This would be cool. Maybe, rebuilding Helgen after I slaughter the punks hanging out there. Hiring your own crew to defend it, with trainers, stores..bars...stuff like that.
Exactly, obviously they cannot allow you to build or renovate your fort just anywhere. The logical choice would be to have certain Forts (namely contested ones on bordering and dangerous areas) with the ability to restore it. The way this works is rather simple. The first step would be to introduce an NPC to the newly cleared area. For that matter the whole goal could be creating a trade route between these outposts and the major cities overseen by the Jarls to unify Skyrim. You can have whole classes of guards and fortifications right down to siege weapons that you can upgrade and outfit in better gear. Whenever an outpost is under attack, a courier will deliver a message to you. These towns are taxed, can produce food and crafting materials for your Hall. Each outpost can have varying resources they specialize in to promote the player to rebuild multiple forts. The concept is to upgrade the Outpost to the highest Tier so it can defend itself and produce income and materials for you. The more Outposts you have connected, the greater the output as a Trade route is established. The more established your town becomes, the greater dangers that attack it. (From Bandits to Elder Dragons)