Thought it might be neat that the ports view, from open world changed over time. For example, a port where no one built any buildings, you might see a vary sparse landscape, whereas another port, with say an Iron Mine, and a bunch of American cotton fields, would show fields of cotton, and maybe the iron mine way in the background. Add shipyards, etc, whatever player built structures are there, so you see from OW view.
Kind of like the cities in Total War change as you build up.
The other idea was disasters. Hurricanes, Volcano's (yes I said Volcanos), tornado's, droughts, etc. Could cause an exciting variation to the game and effect economy and trade greatly.
For example, a drought occurs in the gulf states of America. All crop type fields in ports in that region, take a major hit to production of crops. Suddenly the demand for crops of all kinds hits those areas.
Or a hurricane, hits a region, wiping out buildings and killing production until rebuilt. Oh, the rebuilt part, being a delayed timer, because you need time to clean up first. The port might even close all together for a few days.