The Seraphim are new Pacifista units developed by the Marines’ Special Science Group with the intention of replacing the Seven Warlords of the Sea as one of the Three Great Powers. I am pretty sure that Seraphims aren’t the only group of new Pacifista.
Seraphims in religion are only a group of Angels compared to many. They’re considered the most important because the reside near God’s throne, they’re not powerful as in the fighting sense they just stand still and float 24/7 while Angels and Archangels aren’t considered important but they’re the fighting Angels that carry God’s commands.
If you look here you will see the hierarchy of Angels:
Seraphims are considered the highest in hierarchy but they interact with humanity the least and the more you go down the chain the more they interact with the world and humans. I do not expect 9 classes of SSG New Pacifista, that’s simply too much but a Class of Angels from each sphere/triad is enough and to be expected or even just Seraphims and another class like Archangels. Who could be used to make the Archangels models? I have 3 options on who it could be. But first who are the Archangels? There’s normally 4 of them:
Michael, Gabriel, Raphael and Uriel (Uriel is swapped with Azreal in other abrahamic religions like Islam). I don’t expect the characters to be named these angels names but they would represent them. So let’s get to the possible candidates:
1- The Four Emperors
The Marines has had 4 Yonkos in their hands at different times:
Kaido has been in their custody numerous times so it’s very easy to get his DNA and we have already saw Vegapunk experimenting on him, that’s how he made Momonosuek’s devil fruit in the first place;
Blackbeard has been in their hands at his time when he was a Warlord even it it’s brief period of time;
Shanks has visited the Gorosei more than once so they could have been able to acquire his DNA at that time;
After Whitebeard died his body was in the hands of the Marines and the World Government until he was handed to Shanks; we don’t exactly know if he was given the body right away or waited a bit either way a corpse dead on the battlefield is easy to get a DNA from.
2- The Four Admirals
There are 4 Admirals so the numbers match. They’re World Government employees so it’s very easy to get their DNA and we have seen the Admirals used for Vegapunks research before when he implanted Kizaru’s beams into the Pacifista.
Of course all of the examples I said will have the usual black wings, brown skin, and white hair.
*Theory by Tobi