I only want to comment about the map because everybody else seems to have covered the rest.
I want the AI to move ships around the map better and less predictably. Right now the Mediterranean ocean, Suez canal, Red sea, Arabian sea, to Indonesia is the route that the AI takes virtually every time. It makes this area so cluttered. I understand this is because the current system uses the shortest route possible. However in the real world, navies can't take the same route EVERY time. A weaker navy would perhaps have to go around the cape of Africa or South America instead. The other issue is not only do the AI nations take the same route every time, they constantly send all their fleets on this route with very little regard to how many ships they leave home.
I think it would make the strategic gameplay much more fun if you didn't know which way the AI would go. It would make all those South American and African provinces much more important and valuable. I wouldn't be able to just park a doom fleet in the Red sea and wreck everybody year after year. As the United States, the player would actually have to worry about defending the west coast.
Last but not least, since this route is such a cluster of battles, the AI fleets rarely pass through unscathed. If you do engage any fleets that have passed through this route, they are usually highly damaged and very easy to sink.
I lied, I will comment about one more thing: that is modding. After this game is finished I would love to see it opened up to the modding community. This game is gold, and modding will only make it better. There are so many fun ways modding could go.
That's my two cents. Cheers 🖖