In the latter part of his career it was a weakness because he had to train so hard to retain his ferocity and speed. Without his ferocity and speed he is just a short fighter with short arms. In his younger days he could use it to his advantage as it is more difficult to effectively attack a fighter shorter than yourself. There is a reason why tall fighters are generally less aggressive.
I just submitted a post on the thread asking whether or not Frazier could defeat Tyson, and mentioned Joe's greater experience in dealing with world class opponents his own height as a potential advantage in his favor. Mike was geared for dealing with taller heavyweights, and could tee off with some abandon, not being too concerned with them getting under his right. His power could be largely neutralized by big strong and durable heavyweights, but he was never in danger of losing a decision until Buster Douglas upset him. In Tyson's case, a shorter target might have been more elusive.
You could be right there, prime Mike used his height to slip & get underneath an opponents longer reach & punish him with those ferocious uppercuts, Ali & Holmes (to a lesser extent) were masters at keeping you at distance, using their very long reach, mainly the jab to keep an opponent at bay, Tyson would have to be flawless vs Ali & possibly Holmes too, it could be done, Mike was THAT good, in fact he has a real shot at Holmes, I give that 50/50 (leaning very very slightly towards Tyson just now) but Id favour prime Ali on pts over Mike.