Time for a serious post about this topic.
There's actually a way to make this actually, what I'm gonna talk about won't be how CG should be utilized or how they'll adapt the tone of One Piece, what I'm writing about now is how I think they should adapt this series, and in which format, this of course is all subjective, but if they happened to do it this way, I think I'll be more than content regarding the format.
What I think this series should be about? and why?
Well, first of all let's think what will the series be about, for some reason many people claim that the series would be better if it was its own thing, with its own different story, and only sharing the theme of pirates and the title from the One Piece franchise. What these people don't understand, is the fact that this way of thinking is the primary cause of the failure of several Hollywood adaptations of anime /manga /video games, whenever the author tries to bend the story to make it "more fitting for live action" they fail terribly, because people won't simply watch it when it lost its appeal and what made it unique and special in the first place. People won't accept a series about politics with pirates, and they definitely won't accept a series without super powers, whenever people hear One Piece the goofy and fun adventure story comes to their minds first. Some other people argue and say this series should be about a side story, something like a filler arc, this will probably allow the staff go all out with their crazy ideas and ambitions, while not fearing messing with the beloved source material. I strongly disagree with them, simply because this series while should appeal to the fans of the manga, it should also be accessible to people who are totally new to the franchise, which means that the characters origins is a very pivotal aspect of the series. So, I concluded based on what I said previously that it's for the best for them to adapt the story of the manga, hopefully from the beginning to the end.
My personal ideal format for the series
This is a bit tricky, because this is what potentially decides whether the series will be successful or not, if they fail on this department the series might get cancelled, otherwise, if the formula they follow proves to be successful, then they'll get people's attention and they'll likely have discovered a door leading to them winning the fans' money as they buy their merchandise. First of all, let's think about where they should start, and isn't it an obvious answer that they should start with the very first chapter, this chapter is considered a classic among the fans of the series and it'll definitely hit home for the first time watchers as well. The series should probably be seasonal, nowadays the west is all about seasonal shows that ends with a cliffhanger, One Piece will also definitely suffer from budget and scheduling issues if the series took no breaks. And here we go, it's probably for the best for them to adapt the East Blue saga first, and avoid skipping it for the sake of getting to "the good parts" or anything like that. However, this saga suffers from one major issue, is it enough to ensure fans' support to warrant a second season? Well, I won't answer this question, because it's totally up in the air, and I know for sure that Arlong's park is a very good arc that also represents some of One Piece's genuine strengths, and the barrel promise scene is a pretty good scene to end a season on, and Loguetown arc has some promises for the future that would make people anticipate a second season. But what if this isn't enough? what if these promises are not enough? especially when some of them are very vague, like seeing Dragon but knowing nothing about him, knowing nothing about the seven warlords other than the fact Mihawk is one of them. And for some reason the barrel promise feels too conclusive to hype people for another season. I'll stop running around the bush and mention what the first season should cover, it should in my honest opinion begin with the very first chapter and end with the end of the Alabasta saga, specifically the end of volume 23. And how? Well, the series should adapt one volume for each volume, an episode could potentially be any length between 60 to 90 minutes, ideally 90 minutes, which roughly gives each chapter 9 minutes. The first season would be 23 episodes, that covers both East Blue saga and Baroque Works saga. By the time the 23rd episode ends, ancient weapons and poneglyphs would be revealed, people would get an idea of the importance of the world government, Blackbeard would be mentioned, and much much more. And what a better way to end the first season other than a small teaser of Robin joining from chapter 217, this holds the potential to be one of the best cliffhangers for the first season to end on. Also thematically, in East Blue saga the Strawhats were portrayed as big fish in a small pond, but the Alabasta saga is where the characters are really pushed to their limits for the first time. Well, if the first season covers the first two sagas then what the second season would cover? Of course it'll cover the two sagas immediately afterwards. The second season would cover 22 more volumes in 22 episodes, appropriately ending with volume 45, which has the epic cliffhanger of Ace VS Blackbeard. The reason my idea of the second season supports the 22-23 episodes per season is the fact that many people might consider Skypiea saga a bit weak, while I don't really agree, if an entire season is considered weaker than the previous one, it might cause many people to drop the entire show because the quality started "dropping". That makes the CP9 saga a perfect one to pair with Skypiea, as it makes the season generally end on a good note, and it would definitely avoid people staying skeptical about the new crew member for an entire season. Moreover, it would be too good of an opportunity to start a season and end it with Blackbeard to miss. The third and final season before the time skip should cover from volume 46 to halfway through volume 61, well this makes roughly 15 episodes, which sounds a bit out of order, but please here me out. Wouldn't Thriller Bark need extra budget for all the special looking zombies? Same thing goes for the huge unique cast present in Sabaody, Amazon Lily, Impel Down, and Marineford arcs. If necessary, maybe it's better if they slowed down the pacing a bit to fit more episode, and maybe adapt the ace novel and/or expand on the Strawhats separation arc. Finally, the fourth season would cover from volume 61 to volume 82, which roughly makes 22 episodes, and whether it would cover the entirety of volume 82 or not, I personally think there is no problem. The season would finally introduce us road poneglyphs and start the spark between Luffy and the two emperors.
I think the series should be 60-90 minutes for each episodes, with one volume covered in one episode.
Season 1: 23 episodes, Volumes 01-23
Season 2: 22 episodes, Volumes 24-45