7. Jocasta
Jocasta could be an interesting character to introduce after the Avengers sequel, given that she is a heroic robot who was created by Ultron (the villain in the Avengers sequel). Ultron created Jocasta as a mate for himself in an abandoned aerospace research center in Nassau, Long Island, New York. Ultron based Jocasta on the mind-patterns of Janet Pym - the Wasp and wife of his creator (in the comics, at least) Hank Pym. He also set about transferring Janet's lifeforce in to Jocasta in order to animate his robotic mate. Upon learning that this would kill Janet, Jocasta notified the Avengers of Ultron's plans and they ultimately managed to save her as a result - which, in turn, left Jocasta as nothing more than an inanimate object. Pym took possession of her for the purposes of study and, after a series of events that saw her revived, rejoining Ultron, then betraying him, she was taken by the Collector (giving her a Guardians of the Galaxy link as well). She was then saved by the Avengers and became a member of the team. She has the ability to integrate with computers, superhuman strength, durability and senses, optic cannons, the ability to generate force fields and the ability to create holographic disguises for herself. She's an extremely interesting character who could play a big part in the MCU if she was brought in to it (though her links to Pym may have to be altered).