Listed in 1v1 order if it turns into 1v1s
donut race
light of the revolution robin vs corrupt king avalo pizarro (could be a fun fight, unexpected matchup imo, and robin as a revolutionary ally fits to take down a corrupt king. she also likes cute animals and he has a weird oddly cute cat vibe.)
shipwright franky vs the battleship sanjuan wolf (franky building the ship for a donut race vs sanjuan wolf just standing there sounds hilarious to me, also with their roles its a natural pair i think)
boss jimbei vs champion burgess (both helmsman of their crew, and both have a unique fighting style, with it being a karate vs wrestling match. brick fist vs hado elbow. it would be a real mans fight)
sniper king usopp vs supersonic van augur (the most obvious fight ever in the history of fights. for some crazy reason i think usopp will beat him by taking it into close range. usopp almost beat luffy close range, he could do it)
nami the cat burglar VS crescent moon hunter catarina devon (both use trickery and illusion type stuff, nami is the young and beautiful woman on the crew and devon is a hunter of beautiful young women. devon is hyped as strong too so it gives nami hype to take her out)
groggy ring
master chef sanji vs heavy drinker vasco shot (vasco isn't a "cool" opponent but sanji doesn't always fight those. i think they will fight for the "food and wine pairing" theme. vasco's powers i can't even imagine what they could be, but because he resembles the "blobfish" i wonder if he has some kind of "soft" body to contrast sanji's new ultra hard defense. like sanji kicks him and his foot gets stuck in vasco's stomach or something.)
pirate hunter zoro vs jailer shiryu (zoro is all about confronting things directly, and king in this wano arc is the peak of that with his relentless offense, but shiryu with invisibility and "a scar on the back is a swordsmans shame" being a theme makes him a perfect opponent for zoro, because he will just cheat and not respect zoro's ideals of what a battle is, even moreso than king is doing now)
master doctor chopper vs shinigami doc q (i think theres a reveal coming with doc's horse, maybe a powered up transformation. the two could have a very interesting fight using their chemistry and medicine skills)
soul king brook vs demon sheriff lafitte (they're probably from the same country. brook as a proud upstanding military man and lafitte a corrupt cop. both have interesting powers and id like to see how lafittes hypnosis clashes with brook's soul music.
??? vs ??? (who is blackbeards 10th captain? who is joining the straw hats? comedy guess beast tamer tama vs golden lion shiki)