A lot was made of GSP being opportunistic with fighting Bisping as the MW champ, since he's not a huge MW and his style matches up fairly well in certain ways.
I think what GSP did was amazing, but I do agree that he would be overmatched against the Rockholds and Weidmans of the division. Too much size, reach, etc.
GSP would obviously get crushed by a giant like Jon Jones or Gus. Again, too much height and reach. However, like Bisping, the current champ of the division happens to be an ideal matchup. Not only will GSP not be at a big height and reach disadvantage, he will be the taller man.
Cormier is known for his wrestling, but if GSP can take his time and add another 10 lbs of lean muscle, he has elite defensive wrestling which should nullify DC.
GSP is already far bigger and heavier than skinny deflated 190 lb Anderson that didn't even train that DC could barely damage and spammed takedowns against.
I see GSP winning a kickboxing match on points and taking the LHW title. This is a guy who has stated he can make 155. How sick would it be if GSP won 4 belts.