Bethesda games need a better variety of "monster" in general. One thing I wanted to carry over from Fallout into Skyrim is the Charisma/Intimidation system. In TES, reasoning with people is pitifully nonexistent at best. I wish I could walk into a "Bandit's cave" and convince them to put their weapons down, or for them to convince me to leave. In Skyrim, bandits are just another class of "monster".
It would be better if enemies actually "yield" like they say they do;
"Well then, jolly good fight sir. It was indeed an honorable combat, and I hereby accept your yield. I shall sheathe my sword and hold my Thu'um. Now if you'll just let me pass... oh, you're getting up again.. are you... Sir. Sir, you are raising your sword? What.. okay."
I also wish Fallout would add more to this gameplay mechanic. Using guile, logic, cheating, lies to conquer the enemy when you don't want to fight, or if you just want to employ something other than "stabby shooty" from your arsenal. Convince the bandits you're on their side, then spend the next 24 hours poisoning their food supply, etc.
Aside from that, I'd like "champion monsters" too, that would be cool. I'd also like huge enemies sometimes. I want to swim out to an island and be met with a towering hyrda-behemoth thrice the size of a dragon that scares the shit out of me, sending me running home to my sweet rolls and fire.