Wow, now I feel old. You're right. It got way less common once the junior and super divisions came about. The most recent example that comes to mind is Monster Inoue, who jumped from light flyweight to super to dismantle long-reigning champ Omar Narvaez. Besides him and Hops, I can't think of any more modern dudes who've done it.
Leonard was a welter champ retired, came back and took Hagler's belt. Emile Griffith was welter champ and he took Dick Tiger's middleweight belt. And after Griffith took his middleweight belt Dick Tiger took Jose Torres' light heavyweight belt, not another p4p guy but the man in his division and interesting none the less.
Partial credit from me for Broner only because Paulie was the weakest beltholder at the weight. Same with Roy with Ruiz. Heck of an accomplishment still, don't get me wrong.
No. But you can take the $400k payday, quit after barely throwing any punches and then slink away a beaten, broken, humiliated and emasculated shell of a man like Guillermo Rigondeaux. He will never, ever live this down.
It was easier long ago to move up multiple weightclasses due to the existence of PEDs, and lack of drug testing.