Nate, perhaps Mir's plan was to pace himself for a five-round fight. Takedowns can be tiring, and for someone with cardio that fades after round three, if I were Mir, I'd work a jab and look for a good opening that doesn't get myself brained by the power of Cigano. I think Frank Mir did the best he could for Frank Mir.
I think the person who beats Cigano will need an iron chin, a lot of power and skill in their hands and legs, and the ability to time the perfect strike. I still want to see Mark Hunt get a crack at Cigano. Now, this would probably be the fight where Cigano uses his boxing to open up a trip and submits Hunt, but Hunt has an iron chin and enough power and technique to make it interesting on the feet. Overeem would be another interesting challenger. He could try to hurt Cigano's legs with kicks while looking for an opening to do some damage. I think I'd favor Cigano by TKO because his chin is better, but it would be an interesting fight to see unfold. I'd also like to see Rothwell pick up some wins and get a chance at the title.
Shine, I'm a fan of Cormier's combos. He has picked up a lot at AKA, including some sweet striking skills. I think his speed is comparable to the speed of Velasquez (who has wicked quick hands). And Rylin, Velasquez is taller and usually weighs more than Cormier.
I don't yet know who I'd pick in Velasquez-Dos Santos 2. I can't help but think Cain's chin is a red flag. Kongo rocked him multiple times. Now, Kongo has power in his hands, but Cigano has so much more power in his hands. I can't see Cain wrestling Cigano to the mat and having him there long enough to do a lot of damage. I can see Cain using his quickness to clip and damage Dos Santos. But, can I see Cain finishing Dos Santos? Not unless Dos Santos is hurt going into the fight. (And Dos Santos couldn't even walk a week before the first fight.)
And hey, speaking of heavies, I updated the OP with news about Roy Nelson calling out Brock Lesnar. That would be an interesting fight.