So I think it would be great if once every 4 seasons, at the end of that season, there would be a World cup for national teams. (Like in real life)
Based on the managers Nationality you would get that national team to represent.
It would be like the champions league system, so there would be infinite players that play with USA, FRANCE, ITALY, ....
But obviously if you get USA for example you won't compete against another USA team, in every "world cup" there would be 1 team of each nation. Or up to 64 or 128 teams.

Each manager will get a random squad of players from his country, and everybody would have about the same star level. It will be a tough competition if everybody is kind of equal, but a much more tactical game.

World cup is usually 3 round robin games, and 4 knockout games, so 7 games total. so it could be done in 4-5 days or perhaps with 2 games a day would be faster.

I think it would be a cool feature.