Like I've been saying, I do think Ulti/P1 are too physical for Nami/Usopp in the end. I think they are being reserved for others (i.e. a Big Mom Pirate members or Orochi's side) when they recover from Marco potentially.
I actually think Robin/Chopper are the correct matchups for these 2, simply being more physical fighters who can probably better withstand their attacks.
I'm not entirely sure about Yamato fighting a F6. I still think she might be an opponent lined up for Smoothie or something. Franky v. Sasaki seems way better fit for that, but we'll see. Potentially Whos Who is Brook's? Black Maria im still not sure, she hasn't done anything as of yet. Its also possible other supernova (Killer, Hawkins, Apoo, etc) fight some F6 members.
Idk, but regardless there is a point where the strawhats under the top 4 need to take out significant members of either the Beast Pirates or Big Mom Pirates. There are way too many villains for them to be useless in the end, and its about time they all grow to be extremely formidable