For fight matchups we know the captain is gonna take the captain….so...
Blackbeard v Luffy. This is a given especially since Blackbeard beat Ace (Or killed)
Burgess v (Sanji or Franky) So far Sanji mainly fought Karate masters. I could see Sanji fighting Burgess, but IMO, I really want Sanji to fight someone else. I see Franky taking this one because both are in your face punch for punch Im gonna kick your ass type of guys. Its gonna be interesting to see these guys wrestle around.
Van Auger v (Usopp or Franky) Usopp is a better choice because he's Sogeking and this fight will raise Usopp on different fighting and sniping levels. However Franky is known for using guns as well and having a cross hair on one of his hands. Could go either way.
Doc Q v (Chopper, likley but another could fight him) We only know Doc Q as the Doctor because of his name. As of others fighting him, I can see either Zoro or Brooke (If he joins) fighting him. Doc Q is named, "Shinigami" and he carries around a long item of some sort that is wrapped up, and could either be a Sythe, or a couple of swords. If he truely wields a weapon, I see Zoro fighting him. Shingami v Sword demon Zoro would be nice. For Brooke, it would be interesting to see Shinigami v Someone who is a pile of bones.
Lafitte v (Zoro or Sanji) Again, this character we don't know his abilities. However the cane he possesses can be a sword that is hidden, or the cane itself could be as hard as diamond and can use it as a rapier. I see Zoro fighting him if thats his abilities. One thing we know about Lafitte is he wears tap dance shoes. Tap dancing requires a lot of leg and feet movement, and what better way for a Tap Dancer v Black Leg Sanji. This isn't the first time Sanji would face a dancer, remember Bon Clay? He used Ballet style fighting.
One thing is certain, Oda likes to spring up surprises and throw off a lot of predictions out of the window. Who knows, Robin could face Blackbeard or whatnot.
If the current trend keeps happening, Im sure everyone in the SH crew will be paired up with someone, and with the current arc of thriller bark where he has introduced many characters, Oda could introduce more characters that are involved with the BB Pirates. Same can be said with CP9. We only knew of Blueno, Califa, Kaku, and Lucci, however there were other introduced along the way and almost everyone had someone to fight.