I made a slightly long reddit post about this before, but since it's coming up again, I want to share my two cents on why remaining consistent might be more important to Viz than fixing their "mistakes," both genuine and perceived.
One Piece has to date more than 1,200 named characters, and that's before you get into place names, attack names, lore, devil fruits and other in-universe terminology. Even a casual reader has to keep track of literally hundreds of pieces of new information. Worse still, due to the story taking inspiration from countries and cultures around the world, most of these new words aren't just in straight Japanese. He mixes and matches other tongues with his native one and makes all kinds of puns and jokes. And because Oda is only properly fluent in Japanese, he makes mistakes in his interpretation of other languages and writes them in ways easily misinterpreted when you try to translate them back to English. Essentially, there aren't just thousands of names and terms to keep track of, there are multiple possible interpretations of most of these terms.
If you go to a scanlation archive you will be forced to learn at least two versions of many of the thousands of new, made up words the series is throwing at you. Seriously, there is, to my knowledge, no scanlation done start to finish by a single group. Wherever you go, even with the relatively recent unified efforts to translate the colour version, at some point in the archive one scan group is going to tap out and another is going to jump in with their own spellings, editorial standards (if any) and interpretation of the characters and lore. And so you get taken out of the story as you readjust to all the changed names and words, figure out what corresponds to what and rewire yourself to remember the new versions.
There's frankly enough to keep track of without things changing mid-readthrough.
I read a lot of big fantasy works with lots of weird in-universe words to follow and I'd be pretty wary of it if any of them tried changing what things were called between books. Imagine if The Two Towers released with a note in the frontpages saying Tolkein had changed his mind about the amount of English adaptation in the work and was going to stick closer to the original Elvish instead. Frodo Baggins is now Maura Labingi. Try to keep up.
You wouldn't put up with that. It would sour the whole reading experience. And while I'm interested in learning the background that went into One Piece's creation, for a first readthrough, I just want to have a good time following the story.
I'm willing to put up with painful legacy names like Zolo and even awkward recent decisions like Animal Kingdom Pirates (I've seen Stephen's reasoning for going with Animal Kingdom Pirates, and I accept it and defer to his judgement as a professional translator, but I still think Beasts Pirates sounds better) for the sake of having at least one version of the series that's internally consistent and therefore accessible for new and casual readers. As a hardcore fan, I'm happy that I do know different possible translations for different names and terms, and I've got a long wishlist of changes, updates and different decisions I'd like to see in an eventual revised translation far in the future. But for now, I think going for maximum readability is the best choice, particularly for an official release.
