Could any fighter in history move up a class or two to lightweight and beat a 1977 Roberto Duran. I don't know enough about the lighter weights, or old time fighters to be able to answer this. My hunch is that the answer is no. Nobody beats Duran unless they have a physical advantage on his, like his opponents past 1980 did. Is there any fighter that could move up giving Duran the physical advantage, and still compete.
During Duran's reign at 135, the experts said that Arguello was the one active boxer who was capable of pulling off this stunt, so this idea certainly isn't a novel one. Gomez, at his very best, might have been able to take a good stab at it. He had power, mobility, defensive elusiveness, and he was excellent at picking off body shots. At 5'5," he had a solid build, and would have been a little quicker and faster. While I do expect Duran to take him out, a well prepared Gomez might have made things interesting. (Wilfredo was inexcusably overconfident for Sanchez, and he was irreversibly compromised after the beating Sal inflicted on him.)
I don't think so. Sal was an endurance specialist who liked to come from behind to overtake challengers on the scorecards. Duran however, was known for his stamina, and could beat down opponents with sheer attrition. He showed his championship round power against Bizarro, Leoncio Ortiz, Fernandez and Lampkin, all with clean count outs. Sanchez is a good shout, and he could last the distance, but spotting Duran an early lead would be fatal to his chances of winning, and it's likely Sal doesn't match El Cholo's pace out of the gate.
On a bad night all of the following could maybe pull it off: Sanchez Armstrong Mayweather Pep Arguello Camacho Joan Guzman Chavez
Care to elaborate Ripcity? Personally I think Mayweather would be brutalised, but interestign to heasr a contrasting view.