For now nothing is stated that the Mid Trio and Weak trio are fighting the flying six or the veterans it's just speculations right now, you are also forgetting that Chopper with the help of Brook was easily defeated by Perospero. But apparently you think Chopper can now suddenly fight Perospero in a 1v1
, I'm sorry but Chopper isn't 1v1 any of the flying six or the veterans unless he has major help. Who says the other characters are going to be background characters? You don't know that all, characters like Mont-d'Or, Galette, and Amande are still major players of the BMP even if they aren't veterans. Don't act like the Mid Trio and Weak Trio have to only take on the flying six or the veterans.
Also as I have said this before Carrot in her sulong form will be fighting Perospero not Chopper, Carrot already has a grudge against Perospero and she will defeat him to avenge Pedro.