I do think Queen & Who's Who square off but I think it is highly unlikely that Who's Who takes out Queen. Why Oda is building this up tho, I can't say for certain, tho I have my personal speculations about it. Hypothetically speaking if Who's Who does take out Queen, who takes out Who's Who? coz I'm 100% certain that he isn't joining the alliance's side. With regards to Queen and the Tobi Roppo, that's not really true. The only tobi roppo that has any sort of plot going on with Queen is Who's Who. There is as much set-up for Queen v Drake as there is for Jack v Drake or King v Drake. So not sure why Queen in particular is being picked. Especially since it's now blatantly obvious that F6 are not under Queen.
the fight will probably be a tag team with Drake and Who's Who. Drake will ultimately beat Queen, Who's Who will put in work but be taken out.
Zoro and Sanji can always fight against Kaidou and BM if required after their individual battles with the calamities.
Kaido and Big Mom are the main battle. Any other fights they get should be warm ups. Zoro even said so. If he really didn't care who he fought then he could have probably decided to take on the SMILE army or fight apoo or Queen. The reason he wanted to run away was so he could conserve strength in order to fight kaido.
What u're saying is equivalent to Barto/Cavendish taking out Pica on Dressrosa. There was Kuros vs Diamante but there was very strong history there. Marco has nothing of the sorts with any of the calamities. Moreover we already have that kinda relationship between the Dukes and Jack.
How is Zoro slashing Kaidou a better feat than beating King ^^". I'm not a Zoro fan but if that's the only significant ting he does on wano then damn. Moreover how does that even help with his dream. King is most likely the strongest swordsman on Wano but let's just give King to Marco and give Zoro one badass panel of cutting Kaidou instead ^^". That would be atrocious writing imo. Regardless of whether Zoro fights Kaidou or not, it is written in stars that is gonna play second fiddle to Luffy so there's no stardom there. Zoro v King is a far better option. Zoro can cut Kaidou and the sorts after that if that is indeed Oda's plan.
But given the foreshadowing, Zoro will likely play a major role in the fight. And yes, inflicting major damage on a yonko that even G4 Luffy couldn't hurt would put Zoro above King.