I'm just curious what does this DLC set apart from mere mods? Just the story writing? After so much hate regarding Skyrims writing and story, not many will miss that. I would expect a DLC delivering completly new coding no vanilla mod could provide, like completly new melee mechanics etc.
Despite the much-maligned storytelling and quest design for Skyrim, the game does have a few gems - Bethesda is capable of some good stuff. Hopefully they'll prove it with this new DLC. That said, the DLC does add plenty of new mechanics - crossbows, mounted combat, and more - which can be built upon by the modding community.