Re: Who would you let Joss Whedon kill in Avengers 2?
Killing off characters is so hard to do right in a continuing universe because of their potential connections in further characters and films. Killing off Iron Man, for example, means his character stops existing. Bringing back characters though LMD's or whatever is cheesy and shows a lack of forthought on the part of those who control the universe (Masters of the Universe?).
Iron Man is the biggest name in the MCU, I would be shocked if he died. Minor, yet important, characters are the ones you kill off because they are replacable. Coulson was perfect because he was just a dude, however much we liked him appearing throughout the Phase 1 films. (I am just talking films, not the TV show here. Besides, people have "died" and are resuscitated all the time. This isn't new.)
If someone is going to be killed off it needs to be someone who is already part of a group and unlikely to receive a stand-alone film. Drax comes to mind as a perfect character to sacrifice to destroy Thanos, considering that's his whole deal anyway. (I see the MCU using Thanos for awhile to continue to introduce cosmic charcters but I could easily be wrong on that). Maybe Gamora dies instead further infuriating Drax (if Gamora takes the origin of Moondragon as Drax's daughter).
Director Fury could also die as his role is small and replacable. Besides, he has been replaced in the comics by a number of people including Hill and Stark, two already existing characters.
Killing off a character is just so hard because Marvel has to accept they cannot milk that property for anything else. I'm not sure the characters that have been introduced thus far are tapped to that level yet.