Here is my 'ideal' team for The Avengers 2 based on what happens in the film and based on Captain America, Iron Man, and Thor having their own solo movies and therefore having no real 'storyline obligations' for inclusion in the franchise going forward:
Bruce Banner/The Hulk
Natasha Romanov/Black Widow
Clint Barton/Hawkeye
Vision *
Bucky Barnes/Winter Soldier (replacing Steve Rogers/Captain America)
James Rhodes/War Machine (replacing Tony Star/Iron Man)
Gamora **
Ms. Marvel
* With a personality based on
** Brought in because of her connections to
, and to replace Thor on the team