So with this so when you you lost a big fight they always do 10 rounds fights but it would be great if you could choose how many rounds you want to fight so after a lost you can choose to fight a 8 round to get back into the swing of things and you can do rematch clauses for big fights so if you lose you can choose if you want to rematch with that fighter or choose a different fighter to fight
Rematch clauses might get a bit too confusing as rankings change after a fight and injuries occur quite often, with the ranking changes for championship rematches it would be a bit hard, usually if you are a long reigning champion, the rematch is usually there majority of the time anyway
As for the rounds this would work really well on the new game as you are in complete control of your own fight card so maybe open your cards with 8/6 round bouts