Its just a thought but I really would have liked the idea of having a separate skill set specifically designed for vampires and werewolves. Maybe it could come in the form of a DLC with the requirements being you are one of the two and at a decent enough level (30 maybe?). Completing the quests gives you perks specific to that set to improve on, but you would level up those skills by simply being in those forms and killing or eating things..
Im mostly bringing this up because I am currently playing as a werewolf and at level 63 your not all that tough anymore. You have no armor so you can be in some cases one shotted by the enemy, your fear howl only works up to level 26, and if your character didnt focus on One-handed then they dont deal as much damage. It would just be nice to have a tree that could, say, increase your hand to hand damage (specific to your werewolf form, not your base character), how much damage you could take, or even controlling when you turn.
Vampires could get more lasting benefits from drinking blood and if they progress down the tree enough they may even be able to stave off the suns harmful rays (yes I know it defeats the idea, but maybe having a higher tolerance once you hit the later stages would be welcome). Or there could be a perk that makes it easier to communicate with NPC's even at the higher stages.
So whats you take?