Of those 3 the only 1 you have is Aldo.
Mendes - short notice 7 days for Mendes (a wrestler) to get his cardio and weight into fighting form.
Asking that of any fighter, especially one with a wrestling base, and you may as well just hack a leg off.
So no...not a risk.
Aldo? Yup! You get one fight. But then Conor didn't really have anything to lose, did he? He wasn't the belt holder. Had he lost...he would have gotten his rematch.
Diaz? Nope! No belt on the line. And when he lost, he was given his rematch to atone for it. Had he won the first match, Diaz wouldn't have gotten a rematch with Conor. So...no belt at stake and an easy excuse of it being "the bigger man"
Got anything else?