To make the world more alive, it would feel good to have strong marine npcs or pirate captains, and am not just talking abt the normal ones, i mean there should be some that match you in doriki, haki and ability, some even have devil fruits.
I feel like this would make the world feel more alive, since there would be more strong, threatening enemies to fight aside from bosses.
Also, side sugestion, i think pirate/marine captains should have their own rng names, would also make the world a bit more lively.