Of course it will not be like Half Life 2 because its not scripted and you can change the tides of the battles. If there were political factions like in Morrowind you could support and fight with a certain faction a la Mount and Blade. It would be even better if like Mount and Blade you could capture a city, but I think that may be wishful thinking, and that creates complications where if you were part of a faction you could not access towns that were owned by another faction.
But how could cool would it be if you could alter the political landscape of Skyrim by participating in the most exciting part of politics, the fighting? I once read an article in PC Gamer that says Open RPG comes today lack something big to make the game world more real, and thats politics. Screw the new quest system governed by radiant AI, thats not entertaining, being able to lead a war is.
What do you guys think?