Revamp Foreign policy

It would be cool to add a ‘‘World Stability’’ factor that have impact on trade, GDP, migration, crisis like terrorism, etc and depending wich nation your playing, your impact on this value varies but the impact of this value on you is important if you rely a lot on things like tourism, trade, etc (but if stability affect this directly, low stability will impact this de facto so the effect will be there anyway).

Relation values
Having relation values with world region (like Europe, North America, the Middle East, etc) and relation with them influence migration (if you’re going in huge details, immigration from some part of the world could had more poor people of a particular ideology and so on), trade, tourism and the value of these relations could be affected by different policies you have, events and treaties you can enact: trade deals, ban migration, ambassies (or close embassies), ban weapon sales (or fuel them), etc

It would be cool to have more trade policies, international institution, treaties and type of armed forces, here are some suggestion

trade policies
trade policies related to some economical sectors or to region of the world with particular effect.

international institution
Military alliances (international or ideological or regional) that cost money to contribute, may affect patriot, liberal, conservative, stability, have different cost, ethnic minorities, etc depending on wich alliance you signed on.

Being member of some international institution like the UN or IMF or WTO etc and each institution gives you acces to some policies and blocks some (like if you’re a member of the UN, you cannot use torture or detention without trial, things like that and if you’re a member of IMF you cannot put tarif on trade things like that) and being a member of an institution could give positive effect on some values like Stability/migration/foreign relation for UN and trade and positive for liberals for IMF etc

Armed forces
Conventional military forces are covered and are ok like that. Would be cool to add Mercenaries (cost more, but have lower effect on home moral if you have to use them)

Ideological militias would be interesting too, having the option to create a militia copied on the radical armed group you already put in the game, When you create a militia with them, it raises the members of this particular ideology and fueled out the members of the radical outlaw group to fuel in the militia (a way to cope with the problem by "institutionalisation’’) but it could have side effect depending on wich ideology militia have and if you eventually cancel the policy, you refuel the radical terrorist group instantly.

well that’s a bunch of ideas!

Good ideas, but I think that world stability is reoresented in game by foreign relations.