If we're talking at his best and pumped up for each fight as much as he was for Leonard, then he could absolutely win all of them without question. I think Benitez and Napoles would be close fights, but the Duran that fought Benitez was a shell, while Benitez was fighting better than he'd ever fought before in his greatest fight.
I think if you take both from their best fights at 147, Duran wins. Completely different fighter to the one Benitez did meet later at 154.
I'd love to see the Naploes fight, but again, I think Duran was a bit more durable and it would be a brutal fight.