Re: 5 things you want to see
I'd like to see someone aside from Thor/Odin pick up the the hammer (This could also happen in a future Thor film as well, but not both). I don't want the list of people that can pick up the hammer to be more then Thor, Odin, and this third person (Cap is one choice).
My preferred way of having it happen? Thor gets involved in some sort of brawl, sans hammer and is getting beaten. In a short break in the action, a paramedic hands Mjölnir to Thor, either without words, or something simple "Here." That's it, nobody else wielding the power of Thor or anything like that. While that could be done (and the only person I'd like to see use those powers is either Cap or Odin), it would take away from how important Thor himself is. I'd also like for Thor, in the moment, to not realize what happened and never find the guy again. Just a simple thing.
The other 4 things I want to see?
Hulk speaking more. The Hulk should be more comfortable around the Avengers now, especially Tony. I don't want him to be a chatterbox, but more then 1 line per movie. Maybe 4-5 lines, tops.
Phil Coulson. Come on, Marvel could make it work.
Finally, a reversal of the Hulk/Loki "battle". I want to see Ultron absolutely rip apart the Avengers, and make it clear they either need more help or some new sort of strategy (gives Cap an opening to be the strategist). I want it to feel like all is lost and that they barely survive, let alone win.