I honestly can barely see it Happening. The Monster trio was Always wayyy above the rest. Even if Zoro and Sanji fight calamity's, that doesn't mean that the rest can take on the next strongest.
If we look at EL for example:
Kumadori: 810 Doriki
Fukurou: 800 Doriki
Chopper needed his Monster Point to beat Kumadori and that was a technique he could not controll. And Franky had a hard time with Fukurou.
Zoro and Sanji beat guys who had 2200/2180 Doriki - already almost 3 times as much and this does NOT include their Zoan DF which would boost their Doriki even more. 3000+ atleast. And then you have to take into account that after Zoro and Sanji used Ashura and DJ they completely destroyed them. So they could take out guys with a much higher doriki than that - probably someone with a 4000+ Doriki. Franky and Chopper are not even close to that.
Chopper and Brook had already a fight with Peros and got sh*t on. Peros wasn't even trying. Even Pedro was overwhelmed easily and he is one of the strongest minks and has almost 400mil. bounty. Oven also had the upper hand against Pedro in their one clash. Does someone think brook, Chopper or franky could 1 vs 1 Oven or Daifuku? Oven already caught Chopper before and he couldn't do sh*t against that lol.
Or does someone thing they could have somehow stopped that?
They are pissing themselves just seeing it.
If the Flying Six are all, especially, Zoan types and physical fighters, i don't see them Winning it 1 vs 1 - unless they get some huuuuuge PU's. And they can't win with tricks alone - there is only an Limited amount of Credibility until it gets implausible and ridiculous.
They can fight them 2 vs 1 with PU's - i can buy that, but not 1 vs 1. Non of them knows even Haki.
The only one i could see is Ussope, because he got atleast CoO now and is on the right way to get really strong - he could MAYBE get a 1 vs 1 against a F6, but against the ''weakest/weaker one''.
Ofc Oda can make that happen, but how believable is that?