A feature of Marvel seems to be the various factions that dominate it.
Were I Supes, I'd approach each of them and offer a reward. Inhumans get their own nation. Mutants, their own. Atlantis would be left alone, as would Wakanda and Latveria.
I reckon if he played it smart, he could be allied with a good few of them. Soon, they'd all fall into place, and only a few pesky holdouts would remain.