I have often felt there is a lot more that could be expanded upon with foreign policy in the Democracy games. These are my thoughts after playing through D4 and from earlier additions/mods.
International Co-Operation:
UN - pay full membership & co-operate: popular with liberals, international community.
Only pay in membership
Limited fees
Leave UN - popular with patriots
EU/European integration (can be expanded for other countries African Union etc.) How close ties does one want with Europe, ranging from federalism to ‘no deal’.
NATO: ranging from full dues (2% of GDP for military spending) to leaving altogether.
Membership, or otherwise, of all the above events could then be linked with events that fire. e.g. Russian invasion of Estonia. If you are a NATO member and have paid full dues your economy has a bounce. If you have a small military, your economy is crushed. If you have left NATO, when the event fires you there is no effect, etc.
Just some thoughts.