The Hulk is traditionally one of Marvel's most well-known and beloved heroes, and for the most part the MCU has treated him pretty well. After the initial stumbling block that was 2008's The Incredible Hulk, Edward Norton was replaced with Mark Ruffalo for The Avengers, with the actor killing it in the role ever since (not least in Thor: Ragnarok). But the big problem is that Marvel can't give him another solo movie due to rights issues with Universal.
One way around that in Phase Four is to introduce a different version of the Jade Giant. Obviously, She-Hulk is a necessity, too, but on the legacy side of things why not have Amadeus Cho take over from Bruce Banner, à la the comics? Cho has been around for just over a decade, but since 2015 he has operated as the self-titled "Totally Awesome Hulk."
What would make Cho a breath of fresh air in the MCU is that he is a completely different take on the Jekyll/Hyde dynamic of the Hulk. Instead of fearing "the other guy", Cho embraces the change and loves being a giant green superhero. He's also one of the first Asian-American characters to land his own comic book. Could he be the first Asian lead in a Marvel movie, too? Let's hope so.