The current setup is good as it is.
Even though I think that bigger leagues can have their charm, but I don't want it to be to play fewer matches against each opponent.
I would propose leagues of 16 participants, keeping the matchups as they are.
Another option would be that as it is, each league was made up of several groups so that promotions-relegations were more dynamic.
Example wrote: For example with 1 group of 20p and 28 groups of 10p:
- Premier 20 p.
- Champions 2 groups of 10p. (Champions A and B) - total 2 groups of 10p.
- League 1 to 3 ... with 2 groups A,B each league (each group of 10p) - total 6 groups of 10p
- League 4 to 6 and L7,L8 ... with 4 groups A,B,C,D each league (each group of 10p) - - total 20 groups of 10p.
And always you can add L9 even when only need 1 group.