The only problem with moving everyone like that so quick is... they've been training for their fighter for all this time and now cause of Overeem... everyone would pretty much have to change their gameplan on a whim. Mir can't train for JDS the same as he would for Cain, Werdum just fought at 143... he hasn't had another fight lined up so to get him in fight shape that quick wouldn't be worth it, Bigfoot been training for Nelson... world of difference there. Plus Cain been training for Mir... we're talking like world of difference there too.
Best thing to probably do though... just cancel the title fight and move a preliminary fight to the main card. We're already going to have a number one contendership fight on the card... no sense in ruining that and shuffling everything around. I mean on paper its easy but to actually pull it off with these guys and how they train... not so easy. So UFC 146... unless Overeem can find a way to get an appeal done so he can still fight... just cancel it. Which then means JDS is gonna have to wait a few more months considering how much of a war Cain/Mir could be. Cause then they'd have to get medical clearance then start training, and JDS... well he's just screwed.
And as far as the Lesnar/Overeem fight...
No retroactive penalty is likely. Though Overeem was given a conditional fighter's license to face Brock Lesnar late last year under terms that he would later provide two random tests, failing one of those random tests months later is not likely to change the fight result, Kizer said.
According to him, Overeem passed three urine test and one blood test around the Lesnar fight, and his samples from that time have likely been destroyed since.