Enchant, because enchanting felt too limited in Oblivion.
Adding the enchant skill wouldn't adress that, though, the main cause of this, as I see it, is because Bethesda removed many options for enchanting, no longer are there cast when used enchantments for any type of item, and now weapons only get cast on strike enchantments. And Bethesda really needs to make it so enchanting services are available to players who don't join the Mages Guild. And the way the enchant skill was done in Morrowind, I rarely bothered with it because the difficulty of making decent enchantments made it so that I generally just use enchanting services, sure, it was expensive, but at high levels, that was hardly an issue. Still, it would be nice if the enchant skill returned, but if it were added, it would need to be made better to be worth having.
The more skills there are then the greater the change for the player to specialise, and that’s much more fulfilling than being a master of all skills.
While this is true, increasing the number of skills also means that the skills are harder to balance and it's harder to make sure each skill is a viable choice. And considering that Bethesda has not exactly had a record of making balanced games where all character builds are viable but not too overpowered, I can sort of understand Bethesda not wanting to increase the amount of skills too much.
But anyway, the skills I'd like to see most from previous Elder Scrolls games would probably be spear, and unarmored. Spear because I kind of liked using spears in Morrowind, but I'd say they're a rather underrated weapon choice, and while it's true that they may not have been as good as say... long blades, this was primarily due to the lack of variety in them, and rather than removing them entirely, the solution should be to adress the problem by giving them better variety and making them an option worth choosing. And I want unarmored back because maybe with it, playing characters without armor would really be a viable choice. In Oblivion, you're just sacrificing the defense of armor for absolutely no added benefit. Yes, both skills are ones that were in Morrowind, but that's probably because it's the first Elder Scrolls game I've played, and the one I've played most extensively. Not to mention some of the skills in Daggerfall that were removed in Morrowind seemed kind of pointless, take the creature language skills, for example, as far as I know, all they really did was stop those creatures from attacking you. Maybe they'd be worth taking if they actually let you talk to those creatures, but I can't really see that happening.
I also wouldn't mind seeing medium armor back, though I could understand if Bethesda did not add it, and in any case, without medium armor they can still include armors that would have fallen into that category in Morrowind, they're just added into light or heavy instead.
As far as new skills I'd like added. I'd like to see some new crafting skills in the game, actually, because those are always nice for adding roleplayability to games. Ater all, why shouldn't my character be able to make the things he needs if he so chooses? If nothing else, I'd like to see crafting of armor and weapons and maybe clothing, jewelry and arrows and such added, things that the player can actually use, I can't see letting the player make plates or furniture actually serving any gameplay purpose beyond selling. I mean, I guess it would be good for role-playing, but this isn't the fantasy equivalent of the Sims here, I just can't see my characters becoming generic craftsmen, so crafting skills should focus on items the player can use first and foremost. I suppose maybe a cooking skill would be worthwhile if food was necessary, but since I don't really want that, such a skill would really just be a less useful alternative to alchemy.
Levitate should of been on there!
That's not a skill, though, it's a spell, although I agree that it should return.