A cool read...
"Don’t Add New Characters Unless Absolutely Necessary" With Whedon, any new character will be useful and necessary. I love how Marvel lets characters pay their dues. Coulson was built up and Black Widow put in set up time in IM2. Now, "rookie" Hawkeye has put in his dues and I expect to see a more complex role for him in the future.
"Do Build A Great Villain" I'd love to see Ultron. That would definitely make Hank Pym necessary in the sequel and give a badass grounded villain to play with. Going cosmic again (Thanos) after Guardians of the Galaxy would be too much IMO.
"Figure Out What To Do With Loki" Nothing, let them play with Loki in Thor: The Dark World but it's time to move on in Avengers.
"Don’t Stress The Action Too Much" We want great, quality action but since you can't possibly top Avengers 1, don't try by throwing everything at Avengers 2. I agree that is where sequels can go wrong. Again, Whedon won't let it happen. More angst and heart to go along with some cool action set pieces.
"That All Said, Do What You Want Mr Whedon Sir" Amen to that.