Compromise is the key. Use the idea, but keep it simple. Just pick a fixed list of relatively more likely countries, say the top 20 as defined by the G20. This

Compromise is the key. Use the idea, but keep it simple. Just pick a fixed list of relatively more likely countries, say the top 20 as defined by the G20. This extends and improves the traditional country selector which gives special status to 1 country (the USA) rather than 20. If you think a list of 20 needs to be more dynamic, why is it okay for the legacy list of 1 to be static ?