Able to combine races and have a kid, we can already marry outside of our own race so why not have a kid with both races involved? Perhaps have a custom race where it's a combo of this and that with both active effects and balanced bonuses in between. My friend and I were discussing today about the next DLC and about having a dragon tree like that of Werewolf and Vampire given by Dawnguard. Temp transformation into a dragon would be awesome.
Another would be more non-betrayed Falmer. They say that most were either killed or driven off underground or elsewhere so why not have a Trail of Tears sort of thing going on and have another place where Falmer co-exist with others.
Another addition would have to be being able to grip and pull yourself up with your hands if you have no weapons equipped. I have many times became peeved because the jump isn't even that high in which you can literally take a BIG STEP and you're up but because you must put everything into each jump, you can't make it up there. Add a ledge grab like in AC or Dishonored (if they have it in there but it looks like there is) and help pull yourself up, how about being able to squeeze through openings like in Transformers Fall of Cybertron, you just approach it and activate the scene like how you would interact with everything else.
Another would have to be a parry option, I would love to be able to parry and counter as well against fast attackers such as the Forsworn which even high leveled blocks can't keep you from losing some health from those flurry of attacks. To be able to parry and/or counter would be beautiful and add more fun to combat instead of letting it become repetitive.
Horse whistle like in Assassin's Creed : Brotherhood
That would be fantastic, after finishing the quests you need them for, it would be awesome to no longer have them and anyone else as essential. This goes for the Thieves Guild as well, some I would love to just slaughter to prove my point that I'm not the kind to be talked down to and talked trash about like I'm some sort of weakling. Perhaps even have more dialogue options to essential characters when they threaten us such as "I killed many dragons, mammoths, giants, and even cleared out bandit camps, forsworn settlements, and lairs infested with spiders, ghosts, Falmer, and draugr on my own, I don't have to take pl*** talk from you."