If Kane had resorted back to his monstrous self when he removed the mask again, he would have been the ideal choice. He could have cut promos talking about how occasionally in the past, he's tried to convince himself that he is capable of having normal relationships with other people (relationship with Tori, friendships with X-Pac/RVD/Daniel Bryan, etc.) but it's time once and for all that he just accepts that deep down, he is and will forever be a monster. He could thank the Wyatt Family for helping him finally embrace that. Plus, I think it would be cool to have an established veteran in the group among the other three not-as-familiar faces. But that idea is clearly out the window now (not that I mind, because I'm interested in what they'll do with the corporate Kane.)
Looking over the roster, it's kind of hard to picture anybody dirtied up (most likely) and associating themselves with a group of psychotic hillbillies. Maybe they can go the same route they took with adding Serena to the SES and add a female to the group. That would be interesting and balance things out pretty well (and I can imagine Wyatt's voice referring to someone as his "sister.") Maybe Tamina, she would sure as shit look the part.