Base game
Monkey D. Luffy
Roronoa Zoro
Nami
Usopp
Sanji
Tony Tony Chopper
Nico Robin
Franky
Brook
Jimbei
Yamato
Trafalgar D. Law
Jewelry Bonney
Sabo
Donquixote Doflamingo
Boa Hancock
Shanks
Dracule Mihawk
Buggy
Crocodile
Marshall D. Teach AKA Blackbeard
Kuzan AKA Aokiji
Borsalino AKA Kizaru
Sakazuki AKA Akainu
Koby
Rob Lucci
These are pretty much self explanatory. The only character I feel is in any way a surprise is Jewelry Bonney, and more specifically her inclusion over a certain other Worst Generation pirate who is in the first DLC pack. I prioritized story importance to a degree and Bonney has in a single arc gotten more character development and spotlight than any of the supernovas not named Luffy, Zoro or Law and her abilities could really stand out from the rest of the cast.
DLC pack 1
Portgas D. Ace
Eustass Kid
Carrot
Issho AKA Fujitora
Charlotte Katakuri
I prioritized fan favorites for this one. I honestly wanted to save Kid for a later DLC because dunking on Kid after his recent run-in with Shanks is one of the funniest things you can do but honestly there's no real point other than being mean. I felt that Ace had to be the first DLC character because you can't include him in the base roster but you also can't exclude him from the game because of how much of a fan favorite he is.
DLC pack 2
Bartholomew Kuma
Smoker
Perona
Enel
Marco
Yes, this is another pack of fan favorites. I try to diversify each lineup by having the characters have little in common with each other, down to fighting style and affiliation. Technically I do have two Logia DF users and two Paramecia DF users here but I feel like Smoker and Enel would be very different from each other in terms of fighting style and having Paramecia in common genuinely means nothing.
DLC pack 3
Gecko Moria
Nefertari D. Vivi
Bentham AKA Mr. 2 Bon Kurei
Baby 5
Kikunojo
If the two previous packs consisted of mostly fan favorites, this one is much more out there. I actually have reasons for all of these.
Gecko Moria is not really an out there pick but not exactly a fan favorite and out of the original seven warlords he's easily the one you can justify leaving out the most. Still, not that surprising.
Then Vivi, a beloved character and honorary straw hat pirate... but not exactly a fighter, so you wouldn't necessarily expect her to be included.
Bentham is the closest character to a conventional fan favorite in this lineup and yet that's balanced out by the fact that it's Bentham.
And then the last two characters. Baby 5 is easily the most out there pick in this entire roster, and yet she's a fan favorite and a member of the grand fleet with a fighting style that just screams "make me a fighting game character". I admittedly got the idea for that one from
Cutie Gwen
(sorry for the ping) but it was so brilliant that I couldn't pass up on it.
Then there's Kiku, a fairly popular character from Wano but not exactly that major a character. After Yamato, the denizens of Wano that make the most sense to include are either Oden or Kinemon, so why her of all characters? Well it's a combination of wanting a surprising pick, wanting more women on the roster, and her being actually the most popular of the nine scabbards, surprisingly enough. She's also my personal favorite of the that group and she could call on the others for attacks.
DLC pack 4 - The Legends
Monkey D. Garp
Kaido
Charlotte Linlin AKA Big Mom
Edward Newgate AKA Whitebeard
Imu
So I broke my "no association" rule for this one because this final pack is themed. In case you haven't noticed, I deliberately avoided adding characters from the older generation to the base roster, because like Roger and Rayleigh I believe it's time for the next generation to shine. This is one of the main themes of One Piece. But at the same time I also wanted to include these old legends of the sea as they are cool characters with different abilities. They do have some archetypal similarities toe each other as they're very big powerful characters but you know, it's the final pack and there aren't exactly that many characters like this on the roster, I can afford to do this.
The only exception to this theme is Imu - the shadowy figure who's built up as One Piece's final major antagonist. Why are they here? Well, Imu is all but confirmed to be over an 800 years old immortal, making them older than the other four legends in the pack, and also despite how little we know about the character (I deliberately avoided putting characters we know little about preemptively, this is why Dragon's not on the roster), we do actually have enough of a basis for a summon-based playstyle that includes the Gorosei.
Anyway that's the roster, I'm probably gonna update it as the story progresses and we learn more about some of the major players I excluded as well as get introduced to new characters