Formables ideas:
Korea (North Korea or South Korea)
Soviet Union (Russia)
Ottoman Empire (Turkiye)
European Union (All of the EU Member states)
UK (If deformed, England, Scotland or Wales)
USA (If deformed, all US states and Puerto Rico can form this)
Roman Empire (Italy)
Byzantine Empire (Greece)
Arabia (Saudi Arabia, Qatar, Bahrain, Yemen, Oman or the UAE)
Central American Union (Guatamala, Honduras, El Salvador or Nicaragua)
Caribbean (All of the countries in the Caribbean)
Baltic Union (Latvia, Lithuania or Estonia)
Scandinavia (Sweden, Finland, Norway or Denmark)
Iberia (Portugal or Spain)
China (PRC or ROC)
This is just a list of my formable ideas, but so many more countries from world history could be added, even fake countries or regions could be added as formables! Yeah this is pretty ambitious ngl.
Also love your game! Very cool, five stars.