I think they are opponents of WG mostly
Some of them, before to reach the Kaido, need to show their power. They need to fast defeat them
there is 2,5 calamity, Apoo and 5 TR
Kid and Killer vs Ulti and P1; or Kid vs Apoo, Killer vs P1\Ulti and Nami with Usopp vs Ulti\P1
Drake or Zoro vs WhoisWho
Hawkins and Law vs Queen(thanks to their DF they can survive poison attacks), if not then Law vs WiW and Zoro vs Hawkins
Yamato vs Sasaki
etc. Any alignment is possible, but in general, they are presented on a par with the WG and they should have a fight corresponding to their level.
these guys are like the WG, and I highly doubt that except for M4, among the SH there are people capable of defeating them. It will be either a power-up from the air, or a very stupid set-up fight. Either a pair of fighting against one
I, like everyone else, want a fight for the Strawhats, but not the kind that left more questions than answers.