RoboCup is being held in
Japan this year. They hold an annual soccer comeptition with AIBO robot dogs, walking humanoid robot players, full-size robots, mini-size robots, and simulated robots.
I don't think FIRST should try to go in the whole soccer direction. RoboCup already has the area all staked out. FIRST can come up with nice original games without having to resort to soccer.
Perhaps a soccer theme with goals and such, but probably nothing on the scale of RoboCup.