I think the way boxers get duffed up, and the amount of rounds of sparring they do in preparation for that is another world to that of MMA. By the time a boxer is at Floyd's level, the amount of sparring they've done is off the charts and they're as best (for better or worse by the time they hit their latter years - potential dementia pugilistica) conditioned to take those shots as a human can be. The cumulative damage in boxing is also so much more than MMA as all those softening shots to the head/body can often lead to the K.O's seen in the later rounds, even the most gruelling MMA fights are swift in comparison to the tenderising process of a methodical boxer taking his opponent apart over 30+ minutes of boxing, which is what Floyd often does.
Even accounting for the smaller gloves in MMA and how much quicker they conclude a fight, Conor has been badly rocked by punches from Diaz in both fights. On his best day, Diaz can't punch like Floyd nor does he have the accuracy or speed. I don't know what the equivalency would be between a gloved hand of Diaz in an MMA glove and Floyd in a boxing one (PPI/force etc.) but I doubt Diaz would land with the same velocity and accuracy even allowing for Mayweather being in a bigger and more padded glove. If he's tagging Conor at will for x amount of rounds, I think there's a huge element of risk, much greater than Conor has ever had in his MMA career.
Another thing that comes to mind is that Conor fights long with his chin in the air in MMA. Could he unlearn that and tuck for a boxing match where he quickly realises what he's actually got himself into and very probably his natural fighting instincts come out? Every time Diaz tagged Conor when he was fatigued, Conor's instinct was to try and fire back, he dove for Diaz's leg at the end of their first fight when he realised he was in serious trouble, point being, not once did he shell up or defend himself when faced with adverse conditions. That would be incredibly dangerous if he had the same instinct in a boxing bout.
