1) Kurt Angle in the Austin vs. McMahon era: One thing about the storylines that didn't make sense to me back then was McMahon favoring some really weird characters for champion over Austin when the whole point of the program was that McMahon didn't feel Austin was "corporate" enough. Rock was good in that role, but Dude Love, Undertaker, and Kane? Angle would have been perfect for the role as McMahon's hand picked corporate champion, especially as fresh off his gold medal win as he would have been in 1998.
2) Goldberg in the Rock N Wrestling era: he would have been really young(about 20), but whenever I see Ultimate Warrior stuff I think how much better Goldberg would have been in that role. Similar appeals, except Goldberg had more potential and might have realized it had he come up through the WWF at a young age
3) Bret Hart in the Ruthless Aggression era: I just get goosebumps thinking about Hart vs. Angle, Hart vs. Rock, Hart vs. Cena, Hart vs. Lesnar, and Hart vs. Austin or Michaels in 2002/2003 would have drawn I bet. If he hadn't taken that errant kick from Goldberg, who knows?
I'm sure you've got even better ones though.
Kurt Angle actually was supposed to be around in 1998 but decided against wrestling for a while because of ECW, so thank them. And you're right, he would have been an amazing choice as corporate champion.
I think if Brock hadn't left for 8 years to do UFC then the John Cena would have been lot more tolerable for me, but on the flipside he wouldn't have been 10% of the star he became later, so I'm torn.