As crazy as it sounds this would be an entertaining fight with both having a 50/50 chance at winning. Even though Fedor is the overall better fighter and can take Kimbo down and sub him with ease he probably wont. He will choose to stand and bang and to Fedor that means swing for the fences till someone drops. For that reason Kimbo may very well beat Fedor.
I'm not the biggest Fedor fan but a loss to Kimbo would be HORRIBLE for him and the entire Japanese MMA world. For that reason I say no just let him retire and not make a complete ass of himself.