No offense but that's just silly.
The ten best fighters in the world will have MMA backgrounds (formal or not) you can bet on that. They will also spend their entire careers fighting, many on a daily basis, and training to fight.
I think its highly unlikely for a master of any single traditional martial art to be able to step in the ring with someone who is a trained MMA fighter and win. In fact, the early UFCs proved this to be true.
IMO, there isn't one aikido shihan, whom I can think of, that would survive one round in a professional MMA bout with the top dogs (pick any champion from any matching weight class). The ones that I'm thinking of would certainly have the mental conditioning but their bodies are too broken up, they wouldn't have the physical conditioning, and don't have a complete skillset necessary to fight that sort of fight. To even make the comparison is IMO stupid.
To bring this back around I heard Dan say (I'm going to paraphrase because my memory sucks) "Don't mistake this internal stuff for fighting. The body training can definitely improve your martial skill but if that's all you have, you're going to be immovable/unthrowable/etc. right until you get your ass knocked out. You need more."
Since we're playing the what if game, what if you had some young man with the skills of the top aiki masters along with the conditioning and fight specific training/experience. My guess is that he'd clean up. Point being, I believe (and I may be dreaming) that the aiki skills added to just about anything will make it better including MMA fighting.