Luffy vs Blackbeard (possibly with Koby):
Dawn vs Darkness. Koby shows up if Oda wants Blackbeard to be a mirror of Rocks vs Roger and Garp.
Zoro and Sanji vs Shiryu and Burgess: The Wings of the Pirate King vs the 1st and 2nd Captains of Blackbeard's fleet
Zoro will cut an invisible man: IE, he has to cut "nothing". This has been teased since Alabasta. Zoro fights serious opponents generally, so, yep. Fighting Shiryu also means over coming Sanji's power, invisibility, and Shiryu is more of a tactical fighter, like Sanji. Shiryu saved the BB Pirates from Magellan, just like Sanji saved the Straw Hats from Crocodile: they're good at espionage. This fight will push Zoro to overcome his weakness: sense of direction. Zoro is always lost, him fighting an invisible man is a horrible match up.
Sanji fights more jovial enemies (Bon Kurei, Jabra, Queen). Sanji is the only one in the crew with the durability and regeneration factor, outside of Luffy, strong enough to tank Burgess's attacks. Burgess was already capable of leveling multiple buildings with single punches in Dressrosa, and matching Sabo physically, his shock-wave attacks are going to be incredibly dangerous. Fighting a brutal brawler, like Zoro, is rare for Sanji, but, rather than fight a sly opponent like Mr.2 or Jabra, he'll win with brute strength (and hopefully CoC).
Usopp and Nami vs Van Augur and Catarina Devon:
Usopp's fight is obvious, but should be great. He'll have to max out CoO to deal with warping bullets and warping enemies. However, how the fight ties in with Nami is cool.
Nami is a thief, Catarina steals women's heads and people's appearances. Also, we all know Oda thinks Nami is the hottest girl in the series, so, Catarina is bound to target her. Since Usopp is a known liar, I suspect Nami will have to deal with Caratina pretending to be Usopp, while Augur is shooting bullets all over the place.
Augur can teleport Usopp and Catarina around, to make Nami unable to tell which is which, as well. This fight will rely on trickery and thievery.
Chopper and Karoo vs Doc Q and Stronger:
Here's where the fun begins: it's the battle of the animal mascots (and Doc Q). Kind reindeer doctor on super-fast duck running away from plague-bombing evil doctor riding a half-dead pegasus. WHOOOOOOOOO, NOW THAT'S ONE PIECE. Possible Karoo learns to fly from a Devil Fruit. Karoo eating the Duck Duck Fruit would be FUCKING hilarious.
Vivi and Robin vs Alvaro Pizarro and Laffitte:
Kind princess vs corrupt king. Falsely accused child whose life was destroyed by the government vs brutal sheriff who tortured his inmates. Vivi will receive Kuma's Fruit, and use the Devil Fruit of a kind loving king to defeat the corrupt king Pizarro.
This also let's Robin finally make up for nearly destroying Vivi's country. No idea what Pizarro is capable of, but Laffitte's powers are bad for Robin: he can hypnotize her and make her relive the trauma of Ohara. Laffitte has been shown to fly, and Robin is capable of flight with her wing technique, and had the Wings comment regarding Luffy.
Franky and Jinbei vs Vasco Shot and San Juan Wolf:
Battle for World's Strongest Fishman, and Cola vs Booze, WHOOOOO! Vasco, who most likely has a Liquor Logia or Paramecia (though a Zoan is possible), will be a bad match up for Franky, as he can use liquor to mess with Franky's cyborg body. Franky, the shipwright, also ends up fighting the dude who's known as a battleship.
Jinbei fighting Wadatsumi, the giant fat Fishman dude, foreshadowed Sanjuan Wolf. Jinbei has taken over battleships multiple times in this series, including taking some out escaping Impel Down, and destroying Kaido's ships before the Raid on Onigashima. Sanjuan Wolf is known for walking through the ocean, this is Jinbei's fight. The guy who made the ship fighting with the guy who sails it works well, too.
Brook and Yamato vs Apoo and Aokiji:
The Rock and Roll Ice Bowl.
Brook vs Apoo is why Oda never had them fight in Wano: Apoo is Blackbeard's informant, and sold out both of his crews, most likely. Brook, who values loyalty more than anything, even in death, will fight one of the worst backstabbers in the series in a rock and roll duel. Fuck yes. Brook also has potential connections to Aokiji, and also fights using ice-based techniques.
Aokiji helped destroy an island that broke the law, Ohara, connected to the Ancient History, while Yamato saved Wano, a lawless island connected to the Ancient History. Aokiji was introduced hunting "Devil Child" Nico Robin. Oni in Japan are considered demons, so, here Aokiji will fight another "devil child" in Yamato, the child of the demon/monster/Oni Kaido.
Carrot and Tama vs Caribou and Moria:
Rabbit vs swamp, shadow slaves vs animal slaves. Carrot and Caribou both love sneaking onto ships; Carrot comes from a race that has been discriminated against and sold into slavery, while Caribou sold slaves and tried to kidnap mermaids. If Carrot gets Monet's Fruit, this should be a fun (but stupid) fight. Carrot is fast, but Caribou's Swamp will slow her down. But, she can use Electro to electrocute him. Better match up than you'd think.
Tama and Moria both force people to become their slaves, but Tama celebrates life and respects her animal friends, while Moria views the deal and living as his tools. Tama turns animals into her slaves by feeding them dango; Moria's zombies are freed by being fed salt. Ninjas hide in the shadows, Moria is shadow. Moria lost his crew to the Beast Pirates, Tama's forces are made up of Beast Pirates. Both hate Kaido. Fun match up, I imagine Tama gets aged up for it.
Edit: moved Brook and Jinbei around, since Sir Yasheen is right about Franky probably fighting Sanjuan Wolf (keep forgetting the Franky ship connection somehow).