Hello 
I needed to devise a qualification rules for Poliac Champions League. As hinted before, it will be based on a ranking system that reflects the performance in past Poliac CL seasons. Here's a draft of the rules. Examples and comments are given in quotations.
Ranking system
- The system will be constructed on a rolling basis, taking into count the last 4 editions. Points will be weighted (last edition - 100%, last minus one - 75%, last minus two - 50%, last minus three - 25%).
- Points will be awarded for:
a) 2pts for winning a match
b) 1pt for drawing a match
- in the qualifiers the points will be halved (ie. 1pt for a win and 0.5pt for a draw)
c) 1pt for advancing into each round (group phase, QFs, SFs and Final)
- if qualifiers are played over more than one round, no points are rewarded for advancing to the next qualifying round
d) 1pt for the Final winner
Example of ranking, based on current POLIAC CL (not finished as of the writing):
Qualifications
POLIAC Champions League is played by 16 participants. They first play in group phase (4 groups, double round robin). The top two players of each group enter quarterfinals and from then on the competition is played in play-off mode. Quarterfinals and Semifinals are played over two legs while the Final is a single match.
Automatic participation
- The winner of the last season automatically enters the next season's group phase
- The 3 highest ranked players enter the next season's group phase automatically
- The remaining 12 slots will be subject to qualifications.
For the second season, rule #1 and #2 mean that all semifinalists of season #1 will enter the next season automatically
Note: If the last season's winner is among the top 3 ranked players, the automatic entry is extended for the 4th highest ranked player.
Qualification system
I need to account for the fact that the number of participants is not known in advance. So I have created a generic system, explaining it on the current number of entrants. Depending on the numbers of entrants, I may need to make small adjustments.
Rule of thumb: The ranking system will always decide the order of participants, giving the higher ranked either automatic qualification or seeding in the qualification rounds. Players with no previous POLIAC CL history, will enter with rank points equal to 0
- If the number of entrants is less or equal than the double of the slots available, the highest ranked entrants will get automatic qualification and the remaining participants will be divided into pairs for a single qualification round (2 legs).
- If the number of entrants is greater that than the double of the slots available, two (or more) qualification rounds will be played.
The formula for situation #1:
Qa = (2 * N) - X
Qw = N - Qa
where:
N - number of slots available (ie. slots available after Automatic participation slots are filled)
X - number of participants who enter qualifications
Qa - number of participants who are granted group phase participation without qualifiers
Qw - number of participants who enter group phase by winning their qualifications
Example: 4 slots are for automatic participants, leaving 12 slots available. Currently the number of entrants is 19 (N), therefore:
5 (= 24 - 19) highest ranked players get automatic qualification (Qa) and the remaining 14 (= 19 - 5) players will be divided into pairs and will compete for 7 (Qw) available slots
The formula for situation #2 is:
Q1 = (X - N*2) * 2
Q2 = X - Q1
where:
Q1 - number of players who start qualifications in round 1
Q2 - number of players who start qualifications in round 2
Example. Say there are 35 participants competing for 12 available slots. 22 (= (35-24)*2) lowest ranked will start qualifiers from round #1. 13 (= 35-22) highest ranked entrants will join in round #2. After round #1, there will be 24 (= 13 + 22/2) participants and they will be paired in round #2, finally giving 12 participants of the group phase. If there were 31 entrants, I'd add a "bye" player and do the math for 32 participants.