Interesting thought, but Hardy was supposed to have been clean during his WWE title reigns. Vince would not put the belt on someone who was turning up late and drugged up in these "wellness policy" times. He did have HBK as champ back in the 90s when he had problems, but I cant see this happening in the WWE now, especially not when the program is targetted at kids. We all saw what happened to RVD when he got caught with drugs- he lost the belt. If Jeff was in no condition to perform as champion, he would have had the belt taken away.
As for Scott Hall...he was great back in the day, but even after so many rehab attempts/hospital admissions, firings from companies etc... Hall still cant control himself. The guy is just reliably unreliable. I would have loved to have seen The Bad Guy with the title round his waist, but WCW simply couldnt rely on him to carry the company. It wasnt that he was held down- obviously his friendship with Nash and Hogan meant he was always in favour, but while HBK managed to kick his problems and go on to become a legend, Hall never managed it, and still drinks himself into a stupor to this day, even with all the help he has been given.
It is simply Halls personal demons that stopped him from becoming world champion, he had every other tool required- a great look, size, the ability to talk, and a great finishing move in the Outsiders Edge. It is a shame that we will never know how Hall would have done as World Champion, but he has noone else to blame but himself, he has wasted his own considerable talent.
It is for this reason I simply can't compare him to the likes of Arn Anderson and Dean Malenko when it comes to wrestlers who deserved the title in WCW but never got the chance, because they were held down and not given the opportunities, Hall prevented himself from getting those opportunities and the chance to main event, through his personal demons and inability to stay sober.