Tbh, theres a lot of variables, but will try and logically go through each. Disregarding Kaido and BM at the moment, since at this point I don't believe either will go down solo. This is fucking tough at the moment lol. I will try and cover every possible "likely" matchup based on the villain.
- Luffy vs. Yamato or the "Ace" (I still think there is a major surprise here, in that Yamato is Kaido's strongest subordinate or is the Ace, or that the Ace is a separate person and exists within the crew, and Oda is waiting to bombshell us with that reality. Plus, its clear multiple people will have a shot at Kaido and its likely Kaido isn't Luffy's main battle at first then)
- Zoro OR Marco vs. King (This really depends on what Oda wants to do with Marco. If Marco is there just for support, or to hold off BM with the other Whitebeard Pirates, this is Zoro's battle entirely. If Marco is only present with Izo, then I can see him taking this battle. Zoro is the contender for me though due to being an actual swordsman and his desire to cut "fire")
- Sanji OR Kid vs. Queen (Both have their merits as with the above. Luffy, Kid and Zoro fighting top members of the Beasts Pirates as the Worst Generation "fits", but who knows. Kid getting revenge on Queen also makes sense, but Sanji vs. Queen in terms of their eccentric personalities also makes sense. Kid vs. Queen in terms of mechanical arms is a funny little comparison to make. Who knows?).
- Jinbe OR Neko/Inu vs. Jack (If the above are Zoro/Sanji's fights, then Jinbe surely would take on Jack. But regardless, there is an argument to be made for Inu/Neko getting back at Jack for his onslaught at Zou. Jack is a swordsman it seems, so it would fit for Inu/Neko, unlike Jinbe)
- Law OR Brook OR Zoro vs. Who's Who (This boils down to the fact that we know almost nothing about Who's Who save for that he is a Swordsman. Likely being similar in strength to the All-Stars, I'm not so sure this is Brook's fight, unless he is severely weaker than anticipated or Brook get immense gains during the arc. In that case, I'd chalk it down to Law or Zoro depending on if Marco takes on King and Kid taking on Queen.)
- Kid OR Franky OR Jinbe vs. Sasaki (Again, this is another premade assumption based on Sasaki's build. Maybe Kid and Law are meant to take on Who's Who and Sasaki together, considering their rivalry and both F6 apparently being close to the All-Stars in strength. Again, if Sasaki is severely weaker than expected or if Franky gains a ton of strength, I can see with Franky it being a pretty significant fight. Otherwise, I could also see Jinbe just judging similar builds and the fact that Zoro, Sanji and Jinbe vs. Who's Who, X Drake, and Sasaki sounds "decent" if they are All-Star level pirates).
- Killer OR Sanji vs X Drake (Assuming Drake does not blow his cover or betray Kaido until after he loses a fight, these 2 are what I see the most happening. Both Drake and Sanji are similar in their perverted nature and not being able to handle women it seems. There was a moment were they fought too. Otherwise, Drake and Killer clashed 2 years prior when Killer tried fighting Urouge. Considering their weapons, it may be a great matchup).
- Kid OR Hawkins vs. Apoo (Like Drake, this depends on if Apoo and/or Hawkins flips the switch before Kaido is about to be defeated. Kid vs. Apoo is obvious just from this past chapter, though I wonder if their "rivalry" will lead to anything. Hawkins vs. Apoo just screams weird vs. weird. However, its possible this fight just never happens, and Hawkins/Apoo become allies as they see the tables turning)
- Chopper OR Franky OR Sanji vs. Page One (This one is interesting. I entirely doubt Sanji vs. P1 being a thing, and I agree that he clearly wrecked him, but who knows. Chopper/Franky IMO seems more possible here. Both being physical powerhouses, it makes sense if they fight P1 a very physical type of fighter like Chopper/Franky)
- Nami OR Robin vs. Black Maria (Again, its just based on appearances at this point and the fact that Oda usually does not write protagonist men fighting antagonist women, though the other way around happens. This "seems" like it may be a Nami fight, but it entirely depends on how strong Black Maria is and what her powers are. A lot of this boils down to how the F6 even fight).
- Nami OR Robin OR Carrot vs. Ulti (I can see Carrot and Chopper teaming up against P1/Ulti in an interesting tag team, or I can see both Nami and Robin getting exclusive fights towards the 2 F6 Women, depends)
- Brook OR A Scabbard Samurai (Kawamatsu/Denjiro/Asura/Kiku) vs. the Mimiwarigumi Leader (I think this person will be named and as signficant as Fukurokuju in the future, we'll see. This is also assuming the rest of his group are pushovers/ fodder the Yakuza or unnamed-unique looking samurai or the Minks).
- Robin OR Shinobu OR Raizo vs Fukurokuju (like the above, this assumes the rest of the Onibawanshu will be "fodder" for the lesser characters like the Mink leaders or the Yakuza or something. These 3 have history with Fukurokuju so I see it being one of them.
- Usopp vs Orochi (I'm entirely biased towards this one. "Susanoo, born for the NOSE of Inazagi, slays Orochi. I just can't not seeing this one happen. Also, battle of the cowards lol. Momo can help).
- Kin'emon vs. Kanjuro (IMO, entirely happening. No other matchup honestly works or is as emotional)
- Law OR Marco OR Kid OR Hancock (!) vs. Smoothie (Being the other for sure All-Star level character at Wano, this one is tough. Like I mentioned before, Oda does NOT like making male protagonists fight female antagonists and winning. I struggled a ton until I realized that Koby talks to Drake, who a week or so before, was trying to "capture" Hancock. What if by some unorthodox reason (Sword possibly supporting some pirate groups, infiltrating others), Koby brought Hancock to Wano due to their admiration for Luffy? Hancock vs. Smoothie is something I'd LOVE to see. Otherwise, I struggle with the other 3 even fighting her at all.)
- Carrot OR Worst Generation vs. Perospero (Carrot is obvious, due to her possible revenge for Pedro, but I wonder if she's even strong enough. Other contenders seem to be the Supernova. Law, Kid, Killer, Drake, Hawkins or Apoo could have this battle.
- Izo OR Kiku OR Whitey Bay vs. Campote OR Amande OR Gallette (Again, these characters are the other major female fighters this arc, and I personally struggle to see Oda pitting protagonist men against women. There are no female division commanders in the WB pirates interestingly enough, save for possible one. Kiku (and potentially Izo) both live as women and consider themselves women, so these may be great fights for these 2 characters. Bay would entirely be determined if Oda even cares about her or if she's even present at Wano.
- Law OR Drake vs. Snack (Snack being a swordsman, I can see this fight happening. Kid already was implied to have beaten him, so I can see Snack taking a 3rd L from another supernova like these 2).
- Koby (!) OR Killer OR Hawkins OR Apoo vs. Daifuku/Oven (If Koby shows up as Drakes backup, then I can see him taking on a BM veteran. Otherwise, I see this being left for some of the Worst Generation/Supernovas)
- Those who lose out above vs. Numbers (I personally have no idea what the Numbers will be like. Its implied they have devil fruit powers and are extremely powerful, but who knows at this point who may or may not fight them. Its possible they are also "dumb" fodder, but we'll see. As you can see, there will be plenty of contested spots for battles, so many of those characters can fight someone here)
This is what I got, and what I'm expecting in terms of fights as it goes down.