Khan would be gone inside two rounds. It's revisionist history to suggest that Hatton won easily, Tszyu swept rounds 3-6 and landed some big bombs that Ricky managed to take. Amir isn't anywhere near as durable, and defensively he isn't any better either. He might be gone in the first, but Khan's running style and Tszyu's slow start might see him into the 2nd.
I really find it hard to judge these type of situations, because at the end of the day it comes down to styles, down to the night, down to where the fighters are, down to their game-plans. People can speculate all they want, but at the end of the day, you don't know what would happen until they fought, just like Khan-Peterson, where everyone pre-fight, picked Khan by a landslide.
KT had a sniper right hand, as you say BB he'd be gone early doors IMO. Improved Chin or not don't see him standing up to it.
That right hand was a monster. What hatton did that night was not allow it sufficient room to be used. Closed the space fast and nullified it by being too close. Pretty much the blueprint for how he fought from then on - except maybe Tackie. Not good to watch but effective. Khan doesn't do that. He'd be in range of it. He might look good for a while, as Judah did, but sooner or later....
The blueprint on beating Kostya was constant pressure and mauling. Smother him up close so he could not unleash that monster right hand. Now Khan on the other hand is a fast in and out fighter, the exact prototype of fighter that Kostya would LOVE to time coming in. It would probably take him 1 round to time that right hand and then about 1 or 2 rounds to put Khan to sleep. This is not even jumping on the Khan hate wagon its just a stylistic terrible matchup for him. *edit just noticed it was the Kostya from the Hatton fight, ok it will take him 1 or 2 rounds more then but still the same outcome.
The zoo that Hatton fought wasnt as shot as people made out. Hatton put in a career best performance that night and had to absorb some massive shots that night that Khan simply couldnt take. Hattons inside game, roughing him up, mauling away at him was key to wearing Zoo down. Khans pitter patter inaccurate shots would only encourage Zoo to throw more bombs and shatter Khans less than iron beard!!!