And legalised Necromancy....well ok its legal in Oblivion, but I mean the Mages Guild accepts it!
That way you can reanimate children

Just give me some brute werewolves, the ability to become one, and a great magic and combat experience and I'll be happy.

I say it every time a thread like this comes up..... Editable Map Notes.

This is a good topic.

Let's see... I would really like to see the Climbing skill return. (Thieves scale walls not levitate up over them).

Longer hair for male and female characters.

Absolutely no level-scaling of enemies!! Bandits with Daedric armor?...really?

Scalable regions however would be great to see. I think this was done really well in FNV.

If you're going to include companions, I would give them more substance. Maybe more personal quests to build their back-story or elaborate on their persona.
An approval scale system of sorts. Distinct personalities that may or may not agree with your actions and they will stop you to say so.

No "Goodbye" tag unless you are actually leaving them somewhere to pickup another companion. "Let's move on" or "let’s go" (depending on the character) is more appropriate.

Intelligent leveled enemies. IE: I shouldn't be attacked by a level 3 bandit if I'm level 30.

Lycanthopy and Vampirism are a given.

However, let's build on that. Vampire and Werewolf clans with storyline quests that maybe lead to the hero becoming a leader of one of the clans. Then the hero gets the "honor" of solving problems in the clan itself. IE: Brother "so-in-so" went against your orders to lay low for a while and took sister "such-in-such" with him and wiped out the entire town of "blah-blah". Now every Vamp/Wolf hunter in Skyrim is looking for this den!

On the subject of guild leaders: let's see all guild leaders have quests to them. If the player ascends to the highest rank possible in a guild, they should experience the positives and negatives of the position. Not all at once, but maybe some triggers need to be in place. For example, who you discipline or not. What you did on a mission or not. Did you lie about what you did on a mission or not.

Visible results of the decisions you make - If you decide to save a town or drive out an invasion force and the "mayor" of the town says they will rebuild...Let's see it.
Kvatch always annoyed me.

Also, if horses are included in Skyrim, allow the rider to either knock over or decapitate the dumb bandit who thinks it's a good idea to charge on foot at a 1,200 lb. animal at full gallop.

Although magic can be dual wielded with a weapon, can we see a Rogue type character dual wield daggers or short swords?
Or a warrior with 2 axes?

I would like to see the landscape make sense.
IE: Remember in Oblivion how the city of Leyawiin was layed out? There was no possible way a ship could get into the harbor in the Imperial City. Things like that need to be avoided.

That’s all I can think of now. I'll edit in more if I think of it.

im pretty sure environmental effects like the fireball in the forest was confirmed with the first bit of info they released with GI