8. She-Hulk
Black Widow can't carry the feminine sex appeal of the Marvel Universe all on her lonesome. The character of Jennifer Walters (outside of being a green, immensely strong, feminine machine of destruction), is also a highly educated attorney who often takes on other super humans as clients. This alone could help to bridge her story with others in the MCU. She-Hulk has also, at different points, been a member of the Avengers and S.H.I.E.L.D., so the writers have some leeway as far as how to include her in the overall scheme of things. For the sake of better story telling, they may want to alter the oh-so-convenient "cousin of Bruce Banner" plot point, but a She-Hulk movie has every potential to introduce a strong female lead, tie in nicely to other films and characters and have some jaw-dropper action sequences (especially if she goes savage).