low ring IQ + **** stamina means he is average He can't keep up the pace after round 4-5, his speed is gone after the first rounds
The addition of a Granite Chin wouldn't be enough to elevate Khan's game enough to reach an ATG status. However, when you consider all the legitimate flaws already mentioned in this thread, he has achieved (overachieved) a good deal.
Although better defence or sturdier chin would definetly improve Khan, I would say more pop in his punches would have him more successful. The fact is everyone knows they can't box at long range with Khan so they walk him down taking a few shots to to land their big haymakers. It's the blueprint to beat Khan. If Khan had more pop, fighters would be far more reluctant to take those same shots to land theirs.
That's the blueprint to beat Khan. You can just walk him down. He doesn't look good on the back foot.
Mythical fighter - maybe he fights different if he knows he can take a shot. Maybe as a result he stays with Roach etc etc. Of course, it would make him a more formidable opponent but he would still have limitations.
Khan didn't lose to Peterson. That was such a bs robbery with that pet ref and point deductions that even I , a person that couldn't care less about Khan, was annoyed.