Gimmick. Anybody remember remember Ali vs Inoki?  Wepner vs. Andre the Giant? 


If Money wins, MMA fans will say:  not a fair test; it was Mayweather's sport. If McGregor wins, boxing fans will say: So McGregor, right in his prime, beats up a ring-rusty and ancient Mayweather.  Big deal. 


Something for everybody? How 'bout the loser fights Ronda Rousey? Battle of the greatest losers.