I didn't realize it this until just now, but it's kind of sad that this flick is gonna be so dude-heavy. I wasn't a huge Avengers fan, but I always liked the sprawling motley cast, and while I get why you can't make a solo film around Monica Rambeau, the Wasp, The Scarlet Witch, or She-Hulk (actually I don't get that one), Ms. Marvel or Mockingbird. When you reduce the Avengers to their most marketable elements, all you've got is dudes.
Better people than me can speak on this, but I always thought the less bankable cats--Starfox Quicksilver, The Black Knight, Vision and Wonder-Man (especially those last two)--gave texture to the story. It's actually hard for me to imagine the Avengers without any trace of Vision's relationship with the Scarlet Witch.
I'm not so worried, though. I'm sure they'll introduce all of this in films subsequent sequels. It's a know fact that adding more characters always improves comic book sequels.