It's just a suggestion and just my opinion (although I tend to be insistent when I think something could be better
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Player A wins all others in his group, player B wins also all but player A, A and B proceed to the next stage, case eaten.
That's an easy one, but what about this:
Player A won all his games 2-1 (except a 0-2 vs C)
Player B won all his games 2-1 (except the 1-2 vs A)
Player C won all his games 2-0 (except the 1-2 vs B)
Player D lost all his games.
A, B and C won 3 games each, only 2 of them will make it to the group stage. The fairest way of modding such situation I can think of is to start counting who won more rounds (A=6, B=7, C=7). But A only played 2 rounds vs C and I have no idea what could have happened in a third round between A and C.
If the game B vs C (2-1) was C-B-B, and the game A vs C was C-C-?... Why not to find out what that "?" is?. What if that last round is played and it turns out to be a C-C-A? Does player A really deserve no credit at all for winning the third round while B gets credit for winning the first round?.
Also, what about if someone wins 3-0. What happens then. :/
3 round against every player of your group, 1 round won = 1 point. Therefore you get 3 points for a 3-0, 2 points for a 2-1, 1 point for a 1-2 and 0 points for a 0-3.
We could give points for winner 2-0 (3 points), draw 1-1 (1 point to each), and 0 for lose, like FIFA world cup maybe.
Player A = 9 points
Player B = 4 points
Player C = 4 points
Player D = 0 points
B vs C = 1-1. Who gets the second place in the group?. -> needs a tie breaker match that might bring more timekeeping problems (more headaches for moderators).
At this moment I don't see a difference between 2 rounds with the "2-0 = 3 points, 1-1 = 1 point" option and 2 rounds with the "2-0 = 2 points, 1-1 = 1 point" option.
So, no matter which one you choose, if you play an even number of rounds against the other wormers in your group (2, 4, 6, etc) this ties can happen. If the extra stage in the tournament (the tie breaker games stage) won't bring any timekeeping problems then I see it as an option as valid as playing an odd number of rounds (1, 3, 5, etc).