There is no doubt the only fighter Mayweather missed who was a real threat was Kostya Tszyu at 140lb.
Mayweather could have moved up anytime in 2002/3 to fight him before KT injured his shoulder.
It's interesting that Mayweather fought Bruseles only two months after Tszyu KO'd Mitchell, having not fought since beating Corley in May 2004!! (Why didn't Mayweather fight Tszyu that November?)
None of the other fighters mentioned on that list would have beaten Mayweather.
I'm not sure KT would have either, but he would have been a very dangerous opponent for PBF if they had of met back then, i don't think Floyd wanted any part of Tszyu.
Tszyu losing to Hatton blew any chance of a match up in 2005 anyway.