Considering the release of the newest chapter, it’s fair to assume that the Five Elders must be taken down at somepoint, and seeing as Luffy will be busy with the endgame enemy, that being Imu or Blackbeard, someone will have to defeat the Five Elders somehow. Here are who I believe the Strawhats (+allies) will be fighting to allow Luffy to fight Imu freely:
Ethanbaron V. Nusjuro:
This Gorosei must be defeated by Zoro, and if Zoro can’t handle him he needs to work in tandem with another swordsman (Perhaps Shanks or Mihawk) to Kill this Gorosei, as Zoro cannot achieve his dream without defeating every swordsman in the world. Ethanbaron may very well be the strongest of the Gorosei as it was his immediate job to take down all the pacifista on Egghead when he arrived, which would mean it would make even more sense as the right hand of Luffy to fight E.Baron. Another contender for helping Zoro fight E.Baron is Brook, while Brook is also a swordsman he too can freeze things with a similar ice ability to E.Baron.
Topman Warcury:
Further supporting the possibility of Admiral Kizaru joining the Straw Hat crew, it is very possible that he may fight this saint. He is known as the warrior god of justice, and as Kizaru and Aokiji are both the embodiments of slow and lazy justice respectfully, it would only make sense for them to take on this saint, however there is also a possibility that this saint works in tandem with the concept of Absolute justice Akainu. I do honestly hope the warrior god of justice must fight against or alongside one or two of the admirals as it would make the most sense, to me at least.
Shepherd Ju Peter:
The Shepherd Ju Peter, the symbolic warrior god of agriculture, who owns a fruit that supposedly shreds the earth by eating through it. This Gorosei also seems to be very strong, and was able to almost consume Luffy while he was in his Gear 5 form. This opponent could be taken out by an allied Blackbeard, or Sanji, or both working together. Blackbeard alone has the capability of killing Ju Peter like a bug if the Gorosei hides beneath the earth which appears to be his main ability. The matchup of Sanji with this Gorosei comes from many already made references in the names of Sanji’s moves and the name of Ju Peter. Many of Sanji’s attacks stem from the concept of the devil, comparing Sanji to something or a wolf or a fox, a thief to a Shepherd, the Shepherd in biblical terms will often by a sign of a vessel of the gods, and oftentimes Sanji appears to be a vessel of the devil: He lusts, he smokes, and he acts without thinking often, and often as well he will act in anger.
Marcus Mars:
Marcus Mars beats the Itsumade Yokai transformation, He is the Warrior god of Environment and may possibly have abilities linked to diseases due to the Itsumade supposedly being linked to epidemics. He may be a possible candidate for the Straw Hat Doctor, Tony Tony Chopper, who is in need of a power-up, as his most recent boost in strength would have been the end of the timeskip. As well as this Sanji could also play a role in the defeat of this opponent, as well as perhaps Marco, who is also the embodiment of a mythological bird.
Jaygarcia Saturn:
I would hope to see Franky play a role in the defeat of Saturn, as he is one of the only Straw hats to have attacked him when Luffy was struggling. As well as this if Franky has a role likely Robin will as well, and perhaps Kizaru could do as well.
PS: This is all complete speculation. I’d love to hear the ideas of others!