I am trying my hand at my first alternate universe using only the heavyweight division's historical fighters. The set up is pretty simple:
24 boxers will start in the universe. They are randomly selected from all eras. They are also randomly assigned "years" of experience so that some are already in decline while others are past their prime and the remainder are in their prime. Two fighters will be retired each year, with new fighters entering with a 12 year career ahead of them.
The 24 fighters are set up at first in three randomly determined classes: Contenders, Veterans, and Prospects. The structure will be similar to British soccer leagues, with 8 fighters in each class. At the end of the year, the bottom two fighters will drop to the next lower class, the top two fighters elevated to the next higher class.
Each quarter of the year will see a fighter fight once against an opponent in their class. In the first year, two fighters will get an additional fight to establish a champion at the end of the year.