maybe it should be more like CL
20 teams in 4 groups
5 teams a group =8 matches
number 1 and 2 go on
8 teams = 2 matches
4 teams = 2 matches
2 teams = 1 match
13 matches = same number of matches as present setup.
But more likely the problem will be when playing 3 leaques with players on the same level. It might happen that you run into the same teams in all three leaques if the problem is the amount of players on a server.