If GSP says he could've cut to 155 at his retired older age, he could've beaten Bendo, Frankie or Pettis. And had as much of a chance to beat Silva, as Silva had at beating Jones.
Silva also could've maybe been 3 weight champ.
Frankie could've probably beaten Barao & pettis, but we saw Aldo was a pretty strong counter for him, maybe would've done better against Holloway? Not sure how much better Holloway's TDD is.
If they had lower weight classes at the time, BJ in his prime maybe could have.
All I can really think of at the moment.
GSP had a way, way, waaayyy better chance of beating Silva than Silva did Jones. Both GSP and Jones are bad stylistic matchups for Silva, but Jones also has a significant size advantage there. Silva would have 0 chance. Whereas against GSP Silva had a big length/height/range advantage that definitely would have made things interesting. That combined with Silva's jiu jitsu pedigree could have made life difficult for Georges from top position. I really wish we would have gotten to see that fight.