3. Ms Marvel
Though being a popular character in the comics and a popular Avenger, Ms Marvel, in my opinion (feel free to disagree) is just wrong for this current vision of the Avengers. Ms Marvel (Carol Danvers) is a character who is caught in an explosion of an alien Kree device and saved by Captain Marvel. Because of the explosion, the exposure of energy caused Ms Marvels genetic structure to meld with alien Kree hero Captain Marvels, which effectively turned her into half human, half Kree, taking many of Captain Marvels superpowers. In order to properly introduce the character, you would need to give her her own film, which would be possible, but difficult. You would have to set up and probably show the alien race of the Kree and their native planet Hala and youd also have to introduce the male hero for which she takes her powers, Captain Marvel. Despite this type of other worldly set up being conveyed fairly effectively in Thor (and alien races playing a huge role in The Avengers and Guardians of The Galaxy) it might be too much for the audience to accept and totally believe yet another alien origin story. Thor somehow managed it (some would argue barely) but its my opinion that Thor should probably remain the only alien member of the team, otherwise it would probably be asking too much from the audience. Also, I dont know about you, but Im not a huge fan of superpowers that are ridiculously difficult to even attempt to explain with science, for example being able to fly with no wings, and so far The Avengers has tried to come across as realistically and believably as it can considering Thor is in the line-up. Superman only gets away with it because hes Superman. Maybe Im just being picky, but I think if you are going to include another female superhero (which they should) her powers should be interesting, different and very unique to her. Ms Marvels powers include superhuman strength, speed, stamina, durability and flight. Basically just a cross between Captain America and Thor. A boring choice if you ask me. Plus I have always, always hated both her superhero name and her terrible costume.