I do have a few suggestions to change the league composition that might make it a bit more fun (but will unfortunately change the whole mechanic of how it has worked in the past).
1) The first change will be to limit the trophy variance between players in the first 3 leagues. My suggestion is to allow for bronze league only a 1000 trophy range, for silver league a 2000 trophy range, for gold league a 3000 trophy range and leave the last two leagues unchanged.
- The second change is to make the already unfair system a bit more unfair by giving the winners of a league (that is the kings that is promoted to the next league) an advantage in the next league. Implement the following rules:
a. When a king win a league, group that king with opponents where at least 50% will give him between 50-500 medals.
b. When a king loose a league or stay in the current league, use that king to fulfil option a.
c. When you attack a king within your league give a 20% medal bonus - meaning the king that would have given 50 medals will give 60 medals; the king that would give 500 medals will give 600.
d. Implement the above rules only for the first 3 leagues (bronze, silver and gold)
a. Only the lower leagues are effected where the gem bonus is not that high.
b. This change will allow and promote attacks between members of the league. It might be a bit more fun.
c. In order to win the diamond league - you still need to grow up as was always the case
d. To implement these rules should be very easy as it is only a balancing exercise on the server (and maybe a small one on the client)