I have been considering using a young Jason Mamoa as a modified version of Namor McKenzie. He would be a new mutant like the others, but instead of talking to ocean life or anything like that, his initial powerset would be more akin to waterbending from the Avatar world. Eventually that would progress to bloodbending, and he'd be an antagonist to the team for a while. At some point that might begin to shift, perhaps after he's betrayed by Wilson Fisk or something. He would form a loose alliance with the Avengers at that point, but he probably would not become a bonafide member until much later on, deep into the final Thanos arc.