Spooky, my first thought was that there is only one woman. Ms Marvel would be at the top of my list too, although Mockingbird would be a good low budget alternative since she has links to SHIELD and requires no special effects to implement apart from some wire work for pole vaulting. It may be that Wasp and Ant Man will be making appearances in a sequel. Vision would be really cool too.
I admit, I was never a fan of the Avengers. You put Thor or Hulk next to Hawkeye, the power imbalance is just dopey, although if they 'power down' the movie version of Thor this may improve things. The X-Men seemed to have a better grip on this sort of thing. Still, Iron Man was great and I'm a fan of Cap so I'm looking forwad to this movie.