Reasons i can give you for Sanji vs Avalo.
-Avalo has clout and his own subbordinates, just like Queen. Queen had his own crew basically, and a proper background just like Avalo seems to have as the "Corrupt King" from the North Blue.
-He met one of Sanji's previous opponents, and might even have killed him, giving his fruit to Shyriu since he might have one himself already. That alone could already build a dynamic between Shyriu and Pizarro for instance.
-Sanji usually mocks his opponents based on their personality quirks, specifically those that are somehow a part of their overall abilities. Sanji said he liked to cook up Sea Beasts as a defining factor to cook up Dinosaurs. He called himself "the Hunter" when he met Jabra because Jyabura was a wolf, and so far Avalo seems to behave like a feline sometimes, that could be something related to his powers as a combatant, which is something Sanji could use in his casual trashtalk.
-His first appearance in the post-ts has him eating meat, that could tell us he is the cook of the crew (could also be a reference to Lucky Roo, who is the Cook in the RH Pirates). Also look at the scenario around him, it looks like a storage, perhaps even a kitchen too.
-Ivankov didn't mention him when she was talking about the level 6 prisioners. Does it mean something?
-He is the 4th Ship Captain, which could be a "parallel" to the number four gag, although everyone knows Luffy and Sanji are the main and secondary Captains, respectively.
Which reminds me of another possible parallel: Avalo not only has clout and a background as a North Blue king, he wanted to be the Captain of the crew, and Sanji already has been the Captain of the crew and he always has people praising him and getting led by him wherever he goes. Such as the Flying Fish Riders, the Marines in Punk Hazard, the crew in Zou and WCI, Capone's crew in WCI and many others.. That alone could show us he has the disposition to be among the strongest and be one of most reliable men in BB's crew.
Personality wise, he seems to be cocky, a trashtalker and excessively cruel, someone who you can't always tell how serious he is taking things. Such as Queen acting like Chopper had a chance against him, while laughing at Chopper and trying to kill him in the most disrespectul and cruel way possible. Ever since Jabra, Sanji's opponents have been dudes who have fun with cruelty.
-Him and Shyriu were the only ones not using prison uniform among the Level 6 prisioners who got out of Impel Down. Which again could mean nobody really wanted or could mess with these two.
Sanji vs Pizarro, the Evil/Corrupt King vs the Kindhearted/Selfless King. That could be a battle where Oda starts building up Sanji as a king more open and wide. Thats why we barely know a thing about him as of now.
Even though i understand the appeal of Sanji vs Laffitte and the possibility of Sanji vs Burgess, i think Pizarro just fits perfectly the themes Oda wants to work on Sanji in the future, and is also an opponent that has some similarities with Sanji's previous opponents (everyone knows how Oda opperates, right?)
Laffitte vs Nami is just as a great possibility. Just because Laffitte seems to be too relevant in BB's crew, it doesn't mean he can't fight Nami. Ulti was arguably the Tobiroppo with most interactions with strong characters in Onigashima, and even though Nami didn't fought Ulti in a fair 1vs1, it's pretty clear for me that Oda is trying to put some respect on Nami's name as a combatant. And out of the Monster Trio, Oda always highlights Nami's reliability for the crew the most.
The fact Laffitte has been placed alongside Shyriu in a few moments could just be a shout out to the Romance Dawn, back in those days were Oda didn't had that much great plans for One Piece, but that still marks the start of Oda's lifetime work.
Also, the fact Laffitte seems to rely so much in a hax ability indicates he isn't someone suited to fight Sanji imo, Sanji's opponents always rely on destructive power and great physical attributes.
Anyway, i think it's time to wank the goat Pizarro