You shouldn't be allowed to weigh in on fight night 8 pounds over the division's weight limit so if you fight at 147 you should be allowed to come in over 155lbs so instead of 1 weigh in there should be two one the day before and one before walking into the ring if they weigh more than 8 pounds over the limit the belt shouldn't be won/retained
you'd need to get conformity across the federations, which is unlikely to happen or be maintained if i'm right, and boxing federations are registered as a charity, that's about all the info anyone needs to know that corruption is alive and well in boxing and so, the federations will keep their 'rules' as flexible as possible to allow for whatever
The IBF already do this, they do a second weigh in on the morning of the fight. If a boxer has put on more than 10lbs he fails the second weigh in. This is what happened to Kevin Mitchell in his final eliminator at Wembley last month.
And me, great rule tbh, who needs to hydrate more than 10lbs if ur comfortable at the fighting weight? Maybe more lbs at u go up the weights would also be fair
meaning boxers will be fighting in thier REAL weight class instead of picking on phisically smaller classes to win belts...(Canelo, JCCr ect...)