There should also be a option if a player wants to get promoted to next league or not. As i mostly play in platinum league beacause i am unable to compete with strong players who score really good in diamond league. So when i win in platinum league i get promoted to diamond league and then i have to wait for 3 days to get demoted. Its not fair… Let the player decide if they wants to be promoted or continue the same league !
If what you propose would be implemented, top players would make it impossible for you to win any diamond, platinum or gold league.
So, for that to work, there must be a big enough penalty for anyone that doesn’t want to be promoted.
For example, if you don’t want to get promoted to the diamond league and waste 3 days there, you need to sit out of the leagues for 24h (1/3 of the upper league duration) or 36h (half).