This is just a great, insightful post. Very well stated all the way round. I think too that in the wider scope, the movie is about each hero realizing s/he can't always win by her/himself. Cap can't beat Loki alone: he needs Iron Man's help to bring in a foe that potent. Natasha saves Barton out of loyalty and, we think, affection. And Barton needs her, as it turns out, to save him. Hulk needs Stark to convince him he can control the Other Guy. And so on. Here's why what you're suggesting is impossible. Stan Lee is not an actor, and his presence is immediately disrupting to the audience, who laugh at the gag (if they know who he is) or, alternately, chuckle at his awkward line delivery and hammy mugging. For a grave moment such as the one in the streets of Nuremberg, the last casting decision you want to make is one that will lead to giggling and pointing in the auditorium. But Stan Lee had no hand in creating Captain America. Jack Kirby did, with Joe Simon of course, and for the last 20 years of his life (at least) Jack railed against Stan for stealing the characters that he, Jack, created, and for pretending/lying/defrauding the public that he, Stan, had created them. So, whether Jack's claim to sole authorship of Iron Man, Thor, the Hulk, the X-Men and yes, even Spider-Man, etc. etc., is true, or exaggerated, or complete bollocks, the act of inserting Stan into a major moment for Jack the King Kirby's iconic co-creation, namely Cap, would have been a slight against the King. Sorry, but that's just the way it is. The Kirby fans (including yours truly) would have been incensed, along with, quite likely, the Kirby estate. I was, incidentally, extremely pleased to see Jack's name in the end credits twice, one (with Lee) for The Avengers and one (with Simon) for Captain America.