Re: Who would you let Joss Whedon kill in Avengers 2?
I think Joss did right by both the audience and universe by killing off Coulson in The Avengers (a MCU specific character who we cared about just enough to be emotional).
I also agree that he shouldn't kill off characters for the sake of killing them. But I do think that mortality should visit Captain America in the future. Ultron's death and the creation of Vision could be enough emotional resonance for a sequel. Maybe save Cap's death until after Avengers 2 (Cap 3 or Avengers 3 maybe) and they should probably leave it open for debate whether he is gone for good or not.