I feel like increments on port battle flags should be there.
I think it should be multiplied based on how many flags you have active or how many have you wage before server resets.
The price of the nation should be based on distance to capital, the farther the nation is to capital, the more costly it is.
There should also be operating costs. We have a neutral nation, there should be a reason they exist, certain governments/ or non governments, cannot keep them because the upkeep is too much. There they actually defect from any nation.
And if I want to keep this port I should atleast put some gold in it.
(Pirates should also be allowed to raid for this income) Yarr!
To be actively holding any and all ports should be both be a drawback and a reward(Slightly more than just, we can trade with you)