Every fighter, and namely every champion except Junior Dos Santos cuts down crazy weight to fight men that are hopefully a little smaller than them. BJ, does exactly the opposite looking to challenge himself.
This should be completely irrelevant, no matter what the discussion is.
It's BJs fault for taking fights against much bigger fighters. He can challenge himself at lightweight too -- I really doubt he would beat the top lightweights of today.
The beatings and damage he is taking by fighting these bigger WW guys is probably worse on his body than cutting weight is, anyways.
I don't see it as BJ "challenging" himself against bigger guys. There's plenty of skilled guys out there his own size, he just doesn't want to cut the weight to make 155. Some combination of laziness and stupidity if you ask me.
Edit: that said, I don't see him ever being cut from the UFC. He's just slipping more and more out of relevance. He could have been a gatekeeper at LW at one point I think -- instead he's become a punching bag at WW.