Originally Posted by WarChild

Bruce Lee studied many different styles of martial arts and incorporated what he found worked best for him from each style. Essentially, this is the definition of MMA. There's no reason to doubt that if he were training today, he would have incorporated much of the newer styles in to his arsenal.

Bruce Lee also had amazing reflexes and conditioning. There's no reason to think that if he fought today he wouldn't be very good if not completely dominate in his weight class.

All of this being said, there's a reason that weight classes are used. I don't think we'd be seeing him as a heavy weight champion.