Even with 4 entries match fixing could be advantageous if these four players advance and meet in the draw. Only way to do "country" matches in individual cup-draws is to not allow more than 2 players per country into the draw, and mandate that these always are put on opposite halves. Then of course it would be unfair to individiual athletes from countries like china with many great players.. But I guess it is dependent on how the competition should be viewed.. If it is a competetion between Countries/federations (much like the olympics tend to be, counting "golds" for each country etc.) or if it is a competition between individual athletes.