Imu’s companions are the Gorosei. Blackbeard’s companions are his crew.
They might fight an Admiral.
Honestly, I don't think the Gorosei will primarly stay as Imu's companions or at least not in the way how they were shown in Egghead Island, given how Imu has the ability to summon and revive demon armies. We might be getting demon versions of characters who already died. Iirc,
@Elder Lee Hung even came up with the theory that Imu - or the being behind Imu - might summon the 20 ancient kings of the kingdoms which will act as his real companions.
My point, many "maybes" but that's the point: The final war is unpredictable but with the reveal that Gaban isn't a nameless bum, it gives plenty of room when it comes to speculation, especially Sanji's true ceiling.
Also, winning 1vs1 against an admiral is basically the biggest W in this manga. It's like winning 1vs1 against any Yonko, lol.
EoS Sanji having an extreme diff with Marcus Mars does not make him roughly equal to Roger lmao. Do you really think Roger, or Whitebeard wouldn’t stomp the Gorosei 1 vs 1 when Gaban can easily deal with regen?
Who says Mars will be Sanji's final opponent? An admiral could be his final opponent and that's more than enough considering that they are viewed as complete monsters in the One Piece world.
I don't think beating Mars extreme diff means he's equal to Roger. On the other hand, we don't know if anything happens with Sanji afterwards. Unlike Zoro - who has Mihawk as his ultimate enemy - there's plenty of room for speculation when it comes to Sanji's EOS opponent.
What I am saying is that Sanji's ceiling got huge upgrades. Furthermore, Roger would destroy Mars but how would it look with Demon Mars? Looking at Demon Brogy and Dorry - if both of them are on a completely different level compared to their "light peers", it would make the Gorosei even far more powerful.
I'm certain that the Gorosei are not in their demon form because they'd have horns and wings. I guess that'll happen as well.