One thing I would like to be certain makes it into any future DLC, and I wish was in Dawnguard, but alas, it isn't, has to do with Radiant rewards.
In Dawnguard, when you complete various radiant story quests (Kill random Vampire Leader, etc) you're rewarded with a Random, enchanted item, which is better than gold for certain.
However, here's the problem, you're rewarded with these items, but they're already the items that exist in the vanilla game. How much better would it have been (Particularly for non-enchanters like myself) if the rewards drew random, leveled enchantments, but on the Dawnguard apparel? instead of the old stuff like Orcish, steel, etc, with your highest armor skill determining if you get Heavy or Light Dawnguard armor.
Dawnguard is basically a mod like Moonpath to Elsweyr, anyone skilled enough could have done something similar to Dawnguard, but of course, when it comes out from a company it feels cooler.
It feels cooler because it's integrated better. And any VA work doesn't seem like second grade performance of Lord of the Rings. Content modding died with Oblivion, once VA started becoming a "Necessity", it effectively made "Private expansions" nearly impossible to blend with the main game. Which is, after all, the most important part of any mod that's based around actual TES lore.