A free teleport without ship would be nice for those with not much time to play.
Maybe the option to send ships to other outpost with a fee for a rental crew and maybe a realistic travel time for the chosen distance between thr two ports.
A effect on the speed of the sailsetting, appropriate to the sail damage-percentage to simulate damage to the rigging.
-More variance in the gun sounds
-More momentum for the ship masses
-slower speed of sail setting
-real storms / higher mpact of weather
-moddable UI background
-different paint schemes for the ships
I dont want a strategic meta-game above it.
Just keep adding famous battles from the ACW or if you want to expand it past the ACW, Napoleonic era ( Austerlitz, Waterloo, Leipzig) or maybe even the german/french war from the 19th century.