what you say is illogical. how could hull possibly have played, let alone scored at a PPG pace, in the NHL as a teenager when he wasn't even good enough to make canada's WJC team?
brett hull's track record from 18-23 is a guy who had to play his way into the NCAA from tier II and didn't get there until he was 20. also, he was an overaged 6th round draft pick.
the only hypothetical that could justify what you suggest is if the ghost of christmas future visited brett hull circa 1982 and told him to work on his skating, stop eating so many doughnuts, start jogging, working out, etc.
he had every advantage. his dad was one of the best conditioned NHLers of all time, accounting for era. his uncle was in the league. his brothers all played competitive hockey and were all in much better shape than him. his mother was a professional figure skater. his sister was a competitive track athlete. his younger brother would go on to play professional football. brett should have, and did, know what it takes to maximize his god-given talents. as a teenager, he wasn't ready to do any of that yet, and while he did improve every step of the way, from penticton to UMD to moncton to calgary to st. louis, it took him time to figure out what level he had to reach and stay at. this was a guy who got by on god-given hall of fame talent his entire life. i remember seeing the pictures of hull in penticton from his autobiography: nobody with a beer gut like that could play in the NHL, no matter how great his wrist shot is. all of those people around brett who set an excellent example, none of that hit home enough to get him into and keep him in the league until he was in his early 20s.
there is no "what if" for young hull. maybe he could have gotten into the lineup more if he hadn't been drafted by calgary or had to play for terry crisp, who hated him. but either way, he would have had to play those two years at duluth, and he would have had to start in the AHL. he had to at least get his skating up to a bare minimum NHL standard. so at most, he gets an extra half season in '88 if we put him on a team that doesn't already have mullen, loob, and mcdonald ahead of him, with timmy hunter at fourth line RW.