Wlad, Vitali, Holmes are the guys off the top of my head who would have a chance. Holyfield an outsider choice. If Fury could be the best he's ever been, three times in a row, then maybe him too. But you know he'd **** the bed if he won the first one.
Wladmir Klitschko I think. Height, reach, weight, physical strength knockout power, good footwork, excellent jab / lead hand in general, clinching & spoilery bull****. He has quite a few tools to help him. Mike is at a massive height disadvantage and is too one dimensional, Joe Louis isn't great at cutting off the ring so he's ****ed against Ali and Usyk, Vitali, Liston, Holyfield and Foreman already lost pretty emphatically to the names above, and I don't see Holmes beating Ali or Usyk tbh.
The 8 round stipulation might, indeed, favour Mikey. I've always thought the Mike beats Lennie prime for prime, and he'd not have to worry about has tank against the other two. This is a good shout I'd not thought of...