Son and I are playing a tournament with 8 teams - my son knows the teams better than me, so I let him come up with the rules and we roll to see who plays which side: (unless it's one of the goalies we put a little sticker on one of the players to signify they're they one with the special skill.) we're using all the optional and expanded rules.
We've also implemented a rule for penalty kicks that we've now tried 6 times. The kicker writes where they're kicking and the goalie writes where they're saving. 6 choices Left ground, Left air, center ground and air, right ground and air. It was a fun addition/change.
US - No special rule because we're bad
Argentina - Character gets +2 squares when they're dribbling.
Portugal - Character gets +2 squares when they're dribbling.
England - When passing the ground curve can be a an air pass.
Netherlands - +2 squares when moving.
Spain - Extra pass
Germany - Goalie rolls 2d6 instead of one still saves on 5 or 6.
Brazil - Roll 1d6 on 5/6 they dribble through a player. If fail, they stop in square they left to enter the defender's square.