I may make a longer post or a thread about it, but if I was able to change things, I think for Wano, I would have changed it that the Kurozumi Shogunate was not directly oppressive for the sheer sake of it, but rather, it was pushing to become a strong military society to seek to conquer other lands and such. Which, obviously, would mean Orochi would be quite a different character.
I also think I probably would break up the arc into two different ones. Wano itself as the last chain to Kaido, and then Onigashima, which would probably not be in the giant mountain ranges of Wano and having more to it, like an actual city and such.