Swap ONE current Boxing rule with a Classical one. This could be, for example: 12 round distance to 15, 20 or even 45! Hell, why not unlimited again? Next day weigh ins to Same day Others... Give your choice, and explain how it would change the current world of Boxing. The cleverer or more extreme the better!
Considering that even back in the day top fighters like Kid Chocolate were making $100,000+, I don't think it'd go down well.
Greb was just a battle lusted freak. Bet he would still haggle for loads, though. My rule change might be changing gloves back to caestus. Imagine the shock and sheer insanity - everything the same except caestus being used.
For a serious one, I would change the rules to bring back same day weigh ins. I think the extensive draining that a lot of fighters participate is very harmful, both short term and long term, and affects performance ability.
I like it. Imagine if a Minimum-weight like Wanheng changed his trainer to someone like, I don't know, Roy Jones Jr. That undefeated streak might not end any time soon.
Oh man, i really don't know anymore. Who knows? I thin it was a lounge thing but from about 2008, 2009.