So I've been thinking if it's possible to join the Stormcloaks only to realize Ulfric's an ass and kill him after that at some point of the game (I know you can't just go and kill him at first because he's an important NPC for the main story quests).
I don't want to join the Empire and - in my mind - what would make sense in my character's storyline would be him joining the Stormcloaks at first (because of how the game starts and my character being a Nord and having escaped with Ralof), but later realizing how Ulfric is only after power and how his fight against the Empire might even benefit the Altmers by weakening both forces (Empire and Rebellion). His Talos talk is just an excuse for his actions, as I see it. I really don't like this guy (he's a crazy racist who would do anything for power), but I also don't like what the Empire has become.
Please note that I don't really want spoilers about the plot, I just want to know if it is possible to challenge Ulfric to one-on-one combat "in the Old Nord Way" or just take the Rebellion for myself by assassinating him.