Well, that's hard to say, because it is likely his management would have put him in with different opponents, particularly early in his career. They knew he had a glass jaw, so they put him with light hitters. Maybe if he gets put in with more challenging opponents, he becomes better. Maybe he gets beat up and doesn't do well. Who knows?
I think even with a better chin, Khan would still struggle. His ring IQ is one of the lowest I've ever seen.