2. Captain America
And I still think that Scarlett would be harder to get. Captain America, I don't think really needs much of an explanation as to why he is on this list. He is the face of The Avengers team and of S.H.I.E.L.D. in the MCU. Up until now, we still haven't seen too much of Cap in a present day setting. Yeah, Avengers was set there, but we really didn't get to see the personal story that we want. It might be an integral piece of the puzzle as to how the TV and cinema franchises will connect by having him come onto the series and see that Coulson his biggest, collectors cards-toting fan is in fact alive and well (if he is in fact, alive and well). I don't think it would be too hard to twist Chris Evans' arm into agreeing to make a brief appearance on the Marvel series. From what we know of him and his role, he's up for portraying the First Avenger as many times as Marvel will have him.