To be fair, in Oblivion a pure mage was one of the most overpowered classes you could play simply due to how exploitable some things were. Have a weakness to magic effect on a spell, for example, and it'll effect subsequent spell hits, letting you, with a little build up, do thousands of damage points in a single hit. You could also become completely invulnerable to weapons and magic. But yeah, mages have never seemed to have much put into them.
And yet there's nothing stopping you from using the same spells while still wearing armor and carrying a sword. Sure, armor would reduce your spell effectiveness, but when your armor skill was high enough, your spell effectiveness would be at 95%, and having your spells weakened by 5% doesn't make that much difference in the end, especially when you consider that to avoid this, you'd have zero defense. Sure, you could use shield spells or enchantments, but there's nothing stopping you from doing that with armor too, of course since armor rating was capped at 85, you might not NEED shield spells if your armor and skill in it is good enough since even without such spells, your defense might already be at maximum.
However, the issue of unarmored isn't a problem only mages have to deal with. As with a stealth character you might also choose to go without armor, so really, if we're going to talk about unarmored, the discussion shouldn't be limited just to pure mages, but to anyone who might choose not to wear armor.
There was no automatic dodging. All it would have been was giving unrealistic armour buffs to a character wearing no armour
And yet as I recall, giving unrealistic armor to a character wearing unarmored was exactly what the skill did in Morrowind (sure, the armor bonus didn't work unless you had at least one piece of armor, but it was obviously supposed to work, not working was just a bug. And in any case, it's one that can be worked around by wearing a piece of armor that doesn't encumber you much. And now, it has also been adressed by the Morrowind Code Patch for those who use it.) and I was quite fine with that. Sure, it might not entirely be realistic, but so? Fun and game balance needs to take priority before realism in games, because a game doesn't need to be realistic to entertain people, but it does need to be fun, and proper balance helps to ensure that the game is fun for all legitimate playstyles.
And it's not like letting unarmored players have defense bonuses is the only way to make not wearing armor a valiable tactical choice. If unarmored means missing out on the defense provided by armor, then they should offer unarmored players some kind of perk to make up for this. If we assume that they're going to do like they did with Oblivion and have a combat system without any "to hit" roles, then they could add certain special dodging moves, perhaps similar to the ones added by acrobatics, except these would be restricted by wearing armor. Or maybe they could make it so that wearing armor has a greater impact on movement speed and fatigue, thus players who would rather avoid damage than absorb it might have a real reason to choose unarmored. Really, that's what playing an unarmored character should be about anyway. You wouldn't go into battle without armor and stand in one place soaking up damage, you'd try to avoid damage as much as possible because if someone hits you, you don't have any armor to protect you. It might also help if avoiding combat was more of a viable approach to things, after all, you only need to wear armor if you're expecting a fight, but that's a discussion for another thread.
Also, they need to make sure that unarmored players have access to at least the same amount of clothing slots as armored ones. In Oblivion, the decision to not allow wearing clothing with armor may have seemed somewhat limiting as far as customization is concerned, but from a game balance perspective, I wouldn't say it was a bad idea, as in Morrowind, not wearing armor meant that you missed out on many enchantment slots, as aside from gloves and boots, all clothing items could be worn with armor. Thus, not only could you wear a shirt and pants underneath your cuirass and grieves, you could also wear pauldrons on your shoulders, whereas unarmored players had nothing in the shoulder slot, nor were there any unarmored items that covered the head slot. In Oblivion, by not letting armored players wear shirts or pants and adding hoods, they helped to avoid this somewhat, but the rather baffling decision to make the wrist irons the only unarmored hand items in the game once again gave an unnecessary disadvantage for unarmored players. I do hope that in future Elder Scrolls games, Bethesda can make unarmored a more viable choice. Now, this doesn't mean that going without armor should not have a disadvantage, if you don't wear armor, you should be prepared to suffer from less protection. But if you're going to have an option in the game, it's generally not a bad idea to give players a reason to choose it, and unless that option is hard mode, just an extra challenge isn't really enough reason. If unarmorwed is going to be inferior to wearing armor in every way, then there's not much point in having clothes as items you can equip at all. Not that I'm suggesting Bethesda remove that option, I'd hate it if they did that, all I'm saying is that Bethesda might want to think of ways to make unarmored a more viable choice in the game.