7) Nova
As the Marvel Cinematic Universe grows and continues to shift its focus to events in the wider galaxy, rather than mostly on earth, adding characters that can naturally enhance this is a logical step.
Since the planet Xandar and the Nova Corps have already appeared in Guardians Of The Galaxy, surely the hero himself cannot be far behind, right? Despite being human and of earth like Peter Quill’s Star-Lord, Richard Rider was actually given a remarkable set of powers when he was plucked from New York to take on the identity of Nova.
Having faced Thanos within the pages of several Marvel comics and with Xandar’s people already having suffered at the hands of Thanos in the MCU, there would be plenty of reason for him to join the ongoing conflict.
Add to this the fact that his powers with the Nova Force would be visually striking, and it’s easy to see that Rider would make a great addition to the Marvel Cinematic Universe.