That's wrong because Bret WAS an "advancer" as you call it.
Bret was a technical guy who could be colourful, had an image that played well and showed that someone could work their way up the ranks from a smaller pushed jobber, to a tag team, to the IC to the top... Prior to that, champions were brought in for that purpose... no WWF champ built himself the way Bret did and arguably only Flair did with the NWA, everyone else was groomed until Bret.
Without his look with the shades/pink, the nickname, even down to the cocky hand gestures out to the side... he goes nowhere even with all his technical abilities. He was able to put a package together that got noticed, got over and got him in front of the right opponents to show a "small guy" could do it... Bret never wins the belt...Shawn never moves out of the tag ranks much less the IC picture.
First off, I'm not going to disagree with a bunch of this since Bret did everything you mentioned, but I will say this much. I don't think bret's success had anything to do with Shawn's. HBK broke away from the Rockers in 1991, The same year bret broke away from the Hart Foundation.
Shawn was destined for big things from that moment on IMO. He faced Randy Savage for the world title and was in the IC picture after that. Bret got his push faster, but also Bret was there longer.
Shawn probably would've had much bigger success earlier if it wasn't for the fact that Shawn was a druggy and an ass he would've been bigger sooner imo. Bret and Shawn were making the same run imo, until the steroid bs happened. And No I'm not one of those people who think that Bret only got the belt because of that.
Bret was destined for success, as was Shawn at that time. Bret beat Shawn to most destination because he had a head start and the fact that Shawn was a druggy dick.
The one thing I will say is that Vince had a hard on for Shawn. It's been said by many sources, Vince Russo, Triple H, and Jim Cornette to name a few. That no one has ever treated Vince the way Shawn did and get away with it. HBK always had that in his favor, and I think that would've propelled him to the top, just like Bret's pure talent as a wrestler would've propelled him to the top.
Bret wasn't the first guy to break the mold and go from the tag division it's just the business was changing from the regional scene to the big time national scene. Sid, Windham, Flair, all came from tag teams to become stars. Now WWE didn't really do that, even though Taker started as a tag wrestler. To me Bret was the first but his success didn't lead to Shawn's. Now again that's debatable, but I think saying without a bret hart there'd be no Shawn michaels is a bit speculative at best. Since Vince was in Shawn's back pocket, and it was pretty clear.
As far as being IC champion and transitioning that into success as world champion. Not a big deal. You forgot about Savage there, and Warrior. So I don't know. Do you have a point but even if Bret doesn't exist, I think Shawn goes down the same road here.