Marvel loves to add minor characters into their movies in order to introduce them as major characters later: Hawkeye in Thor, Black Widow in Iron Man 2, Nick Fury in practically everything, as with Agent Coulson, Thanos in Avengers, Falcon in Winter Soldier, War Machine in Iron Man, etc. These characters have been decided by Marvel Studios to be better introduced within an ensemble rather than in a solo movie.
The question is, which Avengers characters could they introduce next? Since Black Panther, Doctor Strange, and Captain Marvel (Mrs. Marvel) are all being considered for solo movies, I've decided to exclude them from the list. However, plenty of Avengers could be introduced to the movies just by using the movies they already have films for, or the films they will most likely release within the next movie phase. So without further ado, the top eight Avengers that Marvel could add to their franchise tomorrow.
Quasar can easily be incorporated into the Avengers, and he even has some easter eggs in the Marvel Universe. Quasar was a guard for Stark Industries, who with the introduction of Maria Hill as a Stark employee could introduce his secret identity Wendell Vaughn. During an attack by A.I.M., an organization we saw in Iron Man 3, Vaughn had to use some powerful alien equipment called Quantum-Bands which granted him powers.
These bands could easily fall into Stark's possessions after the events of Guardians of the Galaxy, and could very well explain why S.H.I.E.L.D. cars were on the set of Guardians of the Galaxy despite the fact that the organization now seems to have disbanded.
Barbara Morse, Agent 19 of S.H.I.E.L.D. is already in the Marvel Universe, but we just never really knew it. With Agent 13 appeared in Captain America: The Winter Soldier, we figure Agent 19 was probably at S.H.I.E.L.D. too. However, with the fall of the organization, she's most likely a freelance agent, which is exactly how she was working when she met Hawkeye in the comics.
Essentially serving as a female alteration on the Vision, Jocasta is a creation from the supervillain Ultron to fulfill his devious plans. However, unlike the Vision, Jocasta was made to be Ultron's mate (I sure hope the Vision wasn't made to be Ultron's mate, but if that's how he swings..).
Jocasta was implanted with the mind and consciousness of Jane van Dyne, AKA the Wasp, who is thought to be introduced in next year's Ant-Man, and later gains an independent consciousness later. She turns against Ultron and joins the Avengers, the same kind of events as the Vision who will be in the next Avengers movie, so she can definitely be adapted to the big screen.
Having a very similar origin to Dr. Strange who is most likely getting his own movie in Phase 3, Dr. Druid gained his powers from the Ancient One, the same entity who granted Strange his own powers. He could even serve as a decent sidekick-esque character in the film if Marvel were to decide to include him in the adaptation.
Druid also has plenty of connections with the Avengers team, having help save the Avengers Mansion, and even being appointed leader of the Secret Defenders by Doctor Strange. With the Defenders becoming a netflix series, introducing this character would supply the possibility for a spin-off Secret Defenders adaptation.
Wonder Man is a superhero that is often overlooked simply because his name sounds a bit shallow. However, Simon Williams would be an amazing addition to the Avengers team, and has an infinitely deeper story than many of the previously adapted characters.
Son of the founder of Williams Industries (rival to Stark Industries and HAMMER Industries), Simon inherited the company after his father's death. However, with his lack of experience, he could not compete with Stark Industries, and ended up stealing money from the company for the sake of investments under advisement from his brother, but was discovered, found guilty in trial, and imprisoned.
Through tragic turn of events, Simon sank to assisting super villains in their attempts to take down the Avengers: after being treated with ionic rays giving him superpowers and joining the Avengers as a double agent, he eventually turned good, and he plays an important part in the development of the Vision.
Swordsman has origins with Hawkeye as a villain turned good, as they both have a history with crazy stunts. Despite having a villainous past, he was permitted onto the team. Unfortunately, in turning good he appeared to be a villain rather a hero. In the comics, he was an Avenger for a very short time, however if Jeremy Renner's Hawkeye contract expires, then his part could easily be rewritten for the Swordsman and introduce this new hero (not that we don't love Hawkeye!)
As brother to the villain of Guardians of the Galaxy and assumed Avengers 3's mad titan Thanos, Star Fox would be an amazing addition to the Avengers team. Being good friends with Captain Mar-Vell, he could also be an essential character for Mrs. Marvel if they so pleased, having him help her to understand her newfound Kree powers after the death of his friend, etc.
Being the brother of the craziest villain of all time and the "final boss" for Avengers 3, he could also be used to reveal one of Thanos' weaknesses to the team that could be used to defeat him despite the fact that Thanos has gained supreme power.
Finally, we have Moondragon. Her father being Drax the Destroyer from the upcoming Guardians of the Galaxy, and having been raised on Titan, the home planet of Starfox and Captain Mar-Vell who is essential to the character Mrs. Marvel who could potentially be getting her own movie soon, Moondragon has more than enough connections to be welcomed into the Marvel Universe.
These characters feel the easiest to incorporate into the movies without any additional solo movies or having to stray too far from the main focus of the movies. However, Marvel most likely won't always be focusing on Avengers, and will likely introduce other characters from other ensemble groups. I hope to post a list of the best potential non-Avengers superheroes to introduce soon.
What do you think of my list? Comment below with your favorites, or who you think should be on the list instead!