Regarding the citizens of a Port, there is not much mechanics to them, but the fact some pay taxes. So I thought of a list of a few mechanics I thought would be good for implementation.

Loyalty
Port Loyalty points are split across the Top 10 nation holders in a specific Port and their influence. In total 1000 points are given per day.

ie: in Regis the most influence nations are.

1 India India 36,215,667
2 Egypt Egypt 29,476,894
3 Isle of Man Isle of Man 1,127,652
4 United States of America United States of America 887,415
5 Russia Russia 831,286
6 Pirates Pirates 715,411
7 Spain Spain 455,365
8 Tokelau Tokelau 326,698
9 Mexico Mexico 242,525
10 Bermuda Bermuda 110,106

So out of 1000 points, India would get the most, then Egypt, then US, Russia, Pirates.. etc.

Loyalty Points
If a nation is overtaken, the nation's population will rebel for 10 days on the invaders. They will lower the influence of the port invaders by x every hour.

x = Amount of port loyalty points the original nation had.

max being 300k influence lost per hour of the attackers. This influence lose is to the nation's influence COMBINED, not seperate players.

ie: If China took Chalkos and Chalkos had 300k loyalty points towards Spain. And China had 5 players all with 50mil influence each in the invasion. That is 250mil influence in total. The citizens every hour lower that influence by 300k. So after the invasion, an hour passes and each of those 5 players lose 60k influence. Then 60k again and again per hour.

Loyal Citizens
If citizens are overtaken by an invader, a percentage of those citizens will leave that port to travel to a new port of their original nation.

ie: Regis is taken, so 50mil citizens will disembark for Pania or other Egyptian ports.
(this is where ships guaranteed for Port activity can play a part. Some guarding those Citizen's voyage to the other ports while the offensive can plunder those voyages and send that population back to their port).

im totally agree about adding some new mechanics about port control.

In my opinion the port system should provide some benefits to young nations. and can be defended buy ships also.

Current system is like who have more voodoo credit or money he win. We should add some diversity. i already read lots of nice advice about port features.

We should gather all ports suggestions under a topic and we should work to get some beneficial solutions.

New mechanics are always interesting but we're already 4 years into ship specialization. I would rather see the devs spend time on game mechanics that are core to the gameplay.