Wow, I just had this exact same idea today! Let any country join as long as they can have a representing team of 5 or so to do crew battles, world cup style. I logged on to post about it but well it looks like you beat me to it.
Here's how it would go down if it were up to me: Any country whose Smash community wishes to join the Smash World Cup will hold a single tournament, with anyone of the corresponding nationality invited to enter, to determine the players on its national team for the World Cup. It would play out as any typical Smash 1v1 tournament, but the champion will be declared the new captain of the national team, and he or she will then pick 4 more players from that tournament join him or her as a 5-player national team.
Any country which manages to form a national Smash team in this manner then registers its team in the World Cup, and specific details on how the World Cup itself will play out would be determined based on time restrictions, space availability, and number of national teams participating. Only two things would be for certain:
1) Every encounter would be a crew battle between two national teams, played under standard crew battle rules.
2) The game used would be either Melee or Project M, as these are the most competitive. Project M even lends itself conveniently by including a Crew Battle stock option so that there is no need for self-destructs at the beginning of each match. Perhaps the World Cup could even be held seperately for both games.
I support such an idea 100%. This would give us in the Smash community something more to get hyped about
. How often, who knows? Maybe yearly, maybe every two years? Regardless how often, I would love to see this happen.