The only thing that worries me is that Big Mom seems loyal, at the moment.
She's obviously waiting for the Red PG and until then she's on Kaido's side.
With the right and anticipated power-up, after Kaido is already damaged (little), 5vs1 could take him down without a logic scandal, but what about the old hag?
Someone must stall Linlin or something big that makes her choose to leave over remain with risk, must happen.
I would love to see old Sengoku and Garp join forces against her, the duo alone without the marines (I think Sakazuki has some defect, he's good in the battlefield, in strength and tactics, but in the mid-long term he's not a strategist and I think he'll do some mistakes like not targeting Wano and the new Gen pirates with the same fury seen against the WB pirates).
I would love to see a Big Mom betrayal and retreat saved by her children, after fatally injuring the two grandpas of the two D pirates here (Luffy's and Law's, in some ways).
Anyway, no way those 5 can bring down two Yonkou, even with Ryu (just see the Scabbards)