I think u should do Turkmenistan, the thing that make it hard it is one of the most weakest countries and you will get attacked by russia multiple time, it will be a big challenge for u
Northern Cyprus. I played it and i lost, but i saw there are multiple opportunities with their respective pros and cons. It would be an interesting challenge
You should definitely play multiplayer it’s so fun you can collaborate with people and anything can happen like I had done multiplayer with Thailand and I got occupied by the us but then Vietnam liberated me and I maneged to conquered the us with Vietnam and China and we won