The thought just crossed my mind he was 5'7 135 lbs If he had commited himselt to Western Boxing fully I believe he would have been a Lightweight champ and a Legend and heres why..

Speed: he had unbelievable hand speed,almost faster than the human eye

Accuracy:He was a deadly accurate striker

Power: His power was legendary,He learned how to utilize every bit of his 135lbs almost superhuman was his power and strength

Footwork:go's without saying and his ability to strike at every percieved angle with maximum power was amazing

Defense: Defense was a priority "Hit without Being hit" is what Bruce preached with Jeet Kune Do

Intelligence: Bruce was a student and a teacher of the fight game he was innovative in his thinking and methods

Bruce was a very physically gifted human being and all joking aside a perfect killing machine...
Again purely speculative Thread but having knwledge of Bruce and studying his Jeet Kune Do for a few years it's a fun thought..

Funny thing is Bruce would never have committed himself to one art,Jeet Kune Do provides a strong foundation by taking the useful attributes of all different arts and blending them all together so you are effecient and profecient at every range of combat..Boxing is the 1st range of Jeet Kune Do.

But boxing alone is considered an incomplete Martial Art system since it is limited..so he never would have committed exclusively though.But we can still speculate