Here's my logic -- this is the Avengers' b-team. All potentially interesting characters on their own (especially Iron Fist), but when they're part of NA, they're second fiddle to the obvious "big guns". And so my casting reflects this -- I picked able supporting players (from ensemble TV shows mostly), to complement my slightly-more-famous main cast.
Having said that...
Michael Vartan as Hawkeye. So far, Vartan is is usually remembered as Agent Vaughn, a key supporting player (and principal romantic interest) on the long-running "spy-fi" drama
Alias. He's got a natural ordinary-Joe charm but can do "ethically gray" convincingly enough to play a well-meaning guy who has been on either side of the law, at various points in his career.
Morena Baccarin as Scarlet Witch. Scarlet Witch is, honestly, a bit of a mess, as a character. She's been portrayed as maternal, sexual, and mentally unstable, depending on who is pulling which of her strings. Baccarin, who played the main "Companion" (read: geisha or courtesan) in the cult sci-fi/Western
Firefly, is well-placed for the role of a character who seemingly embodies so many contradictions, but manages to remain a whole person, in spite of it.
Nicky Katt as Iron Fist. Let me say categorically that I'm against the use of Fist in any NA movie. He's a perfectly interesting character, on his own, or playing off Luke Cage alone. But as part of NA, he's kinda superfluous -- rich guy using his fortune for superheroics? That's Iron Man. Street-level vigilante with personal code of ethics? That's Hawkeye. There's not much room for Danny Rand to stand out, especially while Hawkeye is doing the "resident ninja" gimmick. In spite of my misgivings, I casted Nicky Katt, anyway. Katt has played mostly rough-edged patent bastards in indie films; he seems to be a pet actor of director Richard Linklater, with various supporting roles in
SubUrbia,
Waking Life, and
Dazed and Confused (all helmed by Linklater). But he's also played diamond-in-the-rough type characters, most notably badass teacher Harry Senate on classroom drama
Boston Public.
Jim Broadbent as Jarvis. Veteran British actor Jim Broadbent actually has the range needed to be my choice as both the 616 AND Ultimate versions of Jarvis, no matter how disparate. He's just THAT talented. Obviously, in this version, he needs to be more on the cuddly, paternal side he displayed in the
Bridget Jones movies (as the protagonist's dad), rather than the calculating ring-master he played in, say,
Moulin Rouge. But I trust he'll fit the role, one way or another.