Beta Ray Bill
We’ve seen a lot of strange species in the MCU, but nothing quite as bizarre as a bipedal horse-like alien fighting with a hammer. Despite not hailing from Asgard, Bill is one of the few individuals in the Marvel Universe who is worthy of wielding Thor’s power. After Bill and the God of Thunder fought each other for control of Mjolnir (Bill needed the weapon to defend his people), Odin created a copy of the hammer for Bill called Stormbreaker, which has the same attributes as Mjolnir. Since then Bill has been both an ally to Thor and Earth’s heroes, and roams around the universe helping other alien species. We don’t know what will happen with the Thor franchise after Thor: Ragnarok, but it would be an interesting twist if a non-Norse alien were to inherit Thor’s power in Phase 4 or somehow receive Stormbreaker from Thor himself - who may end up being the only Asgardian who survives the events of the apocalyptic Ragnarok.
Spider-Woman (Jessica Drew)
Spider-Woman shares almost nothing in common with Spider-Man. Jessica Drew gained her powers in utero when she was struck by a beam of radiation that contained the DNA of several types of spiders. After serving as a HYDRA-turned-S.H.I.E.L.D. agent as an adult, Jessica became Spider-Woman to make up for her past sins, and since then has served as an Avenger and agent of S.W.O.R.D. (a counterintelligence agency focused on extraterrestrial threats). In addition to her superhuman strength, flight, adherence to walls and bio-electric energy blasts, Jessica also produces a pheromone that can make men around her feel pleasure. While the general audience might be confused why she doesn’t have any relation to Spider-Man, she still needs to be included in the MCU as one of the Phase 4 superheroes, whether in her own movie or as one of the new Avengers recruits. She has connections with both the superhero world and the spy world, so if we do eventually see her, we can expect a thrilling, action-packed adventure. Also, I'm just over the whole Peter Parker origin story.
Despite popular belief, the cocoon seen in Guardians of the Galaxy did not have Adam Warlock encased within, so the MCU still has yet to even reference the character. Fortunately, the Avengers: Infinity War movies are coming up, meaning that the next few years are the perfect time to introduce him. In the original Infinity War story, Adam gathered up many of Marvel’s heroes (and even a few villains) to help him combat Thanos, who had collected all six Infinity Stones and achieved near-unlimited power. Adam can serve the same purpose in the MCU, both from the big screen and small screen, to put up resistance against the Mad Titan. Being one of Marvel’s most famous cosmic characters, it might be a good idea to have Adam first show up in Guardians of the Galaxy 2, but either way, he’s a must-have for Phase 3. It’s also important to point out that the guy classically has one of the famed Infinity Stones – specifically the Soul Stone – lodged in his forehead, so the character may be key just in that respect.
We’ve seen a lot of Bruce Banner raged out as The Hulk, so why not introduce his cousin, Jennifer Walters, to the Marvel Cinematic Universe? In the comics, Bruce gave Jennifer a blood transfusion when she was nearly killed by a crime boss. His blood, combined with her own personal anger, transformed her into the She-Hulk, and after defeating the criminals that tried to finish her off, she became a superhero. When she is transformed as She-Hulk, Jennifer retains her intellect and also has incredible strength - though is not quite as powerful as her cousin. She has made a name for herself as a strong (figuratively and literally), positive and humorous female character, and has served on teams like the Avengers and Fantastic Four. The blood transfusion angle of her origin might need to be altered to make it more scientifically plausible, but She-Hulk is a super heroine that needs to be adapted for live-action. The cinematic Hulk has a lot of fans out there, so just imagine how they would react until seeing her taking down bad guys and lifting cars and other heavy assorted objects. It would be an amazing sight!
Nova (Richard Rider)
Guardians of the Galaxy introduced the Nova Corps, so it stands to reason that eventually Earth’s representative should be introduced. Although teenager Sam Alexander is wearing the helmet these days in the comics, it should be Richard Rider who is named as the MCU’s first Nova. Chosen by a dying Corpsman, Richard was given the helmet without any instructions on how to use it. Eventually he discovered that it allowed him to connect to the Nova Force, which lets gives him super strength, flight and energy manipulation. He then made a name for himself not only as an Earth superhero, but as an intergalactic defender. Director James Gun has said he won’t include Richard in Guardians of the Galaxy 2, but if the MCU is looking to expand the cosmic side of this universe even more, giving Nova a solo film is one of the best ways to do this. We’ve already met several of the Nova Corps members, so why not let them recruit someone from Earth?