I have been thinking for a long time about how Captain Marvel in The MCU. After a long time of thinking I believe i have came up with a prety good theory that could easily happen in the MCU. My theory is composed of many steps and spans over several movies.
Step one: Introducing [Captain Marvel](movie:949779) character in Age of Ultron
In order for this to work an important character needs to die, Maria Hill. I think it is possible for SHIELD to be rebuilt with Stark in charge, but it is not needed. Shield or no Shield, I believe Stark will need to replace Hill by hiring Carol Danvers AKA Captain Marvel as a replacement. This is a long shot since Age of Ultron is done filming and no one has reported an actress as her role on set, however, all this would require is one small scene of her getting hired
Step 2: Danvers will support Stark in Civil War
I believe that since Danvers works for Stark, she will support him. I do not think she will have powers yet and be against super humans, which would be ironic considering she becomes one. I think she will be an important character, maybe even as important as Coulson was before he "died" in Avengers.
Step 3: Make her go missing in Avengers: Infinity Wars part 1
I believe this will be one of the biggest parts of the movie, with her character being well known by this point. During all the Chaos with the Avengers, i believe she will be captured. My guess is that the Kree are working with Thanos and capture her in the chaos .
Step 4: Give Captain Marvel her powers in her solo movie
I believe her solo movie will start off with her being stuck with the Kree and being experimented on by the Original Captain Marvel where she gains her powers and uses them with the help of the original Captain Marvel to become free where she will go back to earth to help. It would feel like a Scifi spy movie. This would be neat because it would contain important characters and be interesting
Step 5: Bring her back to earth to help defeat Thanos
This would be epic because she will finally have her powers and possibly have a key role in defeating Thanos. She is a neat character and deserves to be depicted amazingly on the big screen. I think it would be amazing if she was depicted as a key in defeating Thanos