You can say the same for Nate Robinson based on that logic. Nate is 5’9”, 180 pounds. Say if he can cut to 155 or 170 lbs, fully trained in MMA with the same athleticism he had during his peak, would he be just as prospected as a MMA threat like Lebron?
Athletically, Nate’s athleticism is equivalent to Lebron’s, if not more. Lebron just happens to be the better basketball player due to height and structure. 5’9” and 6’8” is a tremendous difference in any sport, especially basketball.
To conclude this logic, Lebron’s athleticism does not equate to being a potential gifted MMA fighter. Nate can do it now if he wants, but will he be trained to take a punch to the face? Like GSP said, fighting is 90% mental and 10% physical.