I'm guessing that CP0 will be defeated and our MCs will gain control of the seraphim.
The set up is obvious.
Kizaru with his awakening vs Luffy and the Straw Hats, the seraphim, Bonney, and all of the Vegapunks.
An extreme difficulty fight where a combination of tactics and coordination is needed to repel the Yellow Monkey.
Even if CPO was defeated... Saturn can return the control of them back to the marines.
I figured it would be like this...
Kizaru Vs. Luffy
Sanji Vs. Jinbei Seraphim
Zoro Vs. Mihawk Seraphim
Jinbei Vs. Boa Seraphim
Kuma and Bonny Vs. Kuma Seraphim
Lucci, Kaku, and Stussy attempt to fight the Vice Admirals and the marines on the battleships.
Two things that would seem to need to happen include 1) Saturn will return control of the Seraphim to the navy, and 2) Lucci, Kaku, and Stussy, aside from Sanji and possibly Nami, are the only ones capable of flight. Jinbei could swim to them, but I think he may have to contend with one of the Seraphim because they are former warlords. Luffy can "fly" too, but I doubt he's going to be able to stop all the battleships while he has to deal with Kizaru.
And this all assumes Saturn himself won't enter the fights, but who knows? It's not as though the Five Elders told the world they refused to use Devil Fruits... Right?
You also have to assume Kuma will somehow show up to Egghead to fight alongside Bonny.