I one day wanna see a One Piece AU where everyone actually speaks different languages. Like, perhaps there’s a language that’s spoken in 95% of the world and everyone is bilingual. Luffy, Usopp, Zoro, and Nami all speak an East Blue dialect but even then they have slightly different words because every island is just slightly different, like every English speaking nation. Luffy occasionally throws in words from a noble language that they all think is really odd until they meet Sabo.
Sanji speaks three languages, having picked up the East dialect after running away from North Blue. Franky, Brook, and Chopper don’t speak any Eastern dialects at all and only speak the standard language. Brook used to speak a Western dialect but has since forgotten. Robin knows a bit of everything and is always learning more languages; the national language of Ohara is something she treasures.
The Celestial Dragons have their own language which is “holy” and no one but them is allowed to speak it. Law can only say two things in their language: “shit” and “fuck”. Also, imagine Flevance having its own language and Law is the only one who speaks it now. And Luffy calls him Torao because Law’s accent is difficult for Luffy to understand.
And accents! Everyone on the Grand Line has an accent. You can tell what sea they’re from just because of their accent. South Blue is different to North Blue to West Blue and so on.