It would be a big mistake for Spider-Man 4 to be the mechanism that introduces Mutants into the MCU at large. There are a number of fan theories that Spider-Man: Brand New Day will bring the X-Men or some Mutant characters into the setting. However, there is one big reason why this would be a bad idea beyond it ignoring earlier shows and movies.
Department of Damage Control. (Bill Metzger was an anti-Mutant activist in the X-Men comics.) Finally, there is a related theory that the mystery character played by Sadie Sink is Jean Grey.
The chief problem with these theories is they act like Mutants appearing in Brand New Day would be some shocking revelation. These theories ignore that earlier MCU productions already confirmed the existence of Mutants on the main Earth. These examples stand apart from the appearances of Mutant heroes from other realities, including Beast in The Marvels.
Black Panther: Wakanda Forever confirmed that Namor had powers that were unusual for the Talokanil people. More, he used the word “mutant” to describe himself. Another notable tease came in Ms. Marvel, where Bruno determined that Kamala Khan had a “mutation” in her genes. More, the classic sting from the X-Men Animated Series played at that moment.
It’s also possible that the MCU Wonder Man might be a Mutant. In the comics, Simon Williams gained his powers through scientific experimentation. However, no explanation was given for how Williams gained his energy powers as a child on the show. And the first manifestation of his powers, which set the family kitchen on fire, resembles that of many X-Men members. Beyond that, the Wonder Man series also showed that the Department of Damage Control was now hunting potentially superpowered individuals rather than reacting to them. This is not dissimilar from the American government’s treatment of Mutants in the X-Men comics.
Why Spider-Man 4 should stay focused on Peter Parker instead of introducing mutants
The Punisher, The Hulk and the Hand clan of ninjas and that is a lot to balance even ignoring rumors of a Daredevil cameo. Adding Jean Grey and a subplot about the emergence of Mutants would distract from everything Peter Parker is dealing with.
