My idea would be give you your own flag, they could even make more nations in terms of flags and signups, just your league would be mixed.
It would be good to look over the combined league structure after every season. Perhaps 2+ seasons of stability in users would be the basis of moving any country out of the combined league. What would be the number of users needed to consider a country stable? 80? 336? How many countrys atm are over 336 active users?