Richard Rider, aka Nova, has been part of the Guardians of the Galaxy in the comics. Despite the MCU having explored the idea of bringing the character to live-action and James Gunn's original Guardians of the Galaxy movie having featured the Nova Corps prominently, the director never included Rider because he felt there should be only one human on the team, Chris Pratt's Star-Lord. I would have loved to see Nova in the MCU, but I agree with Gunn, as every member of the team being unique played out for the best. Nova would have taken focus away from Star-Lord.
