Eh, I'm still not of the belief that they are that powerful.
Anyway if they are, I see them losing to people like Kid and stuff instead if they are really all that.
The literal point of luffy's greatest strength is that he draws in strong allies. Kid and stuff are the future yonkou, they'll be doing the heavy lifting. Zoro will defeat kizaru to parallel rayleigh's fight at sabondy, while Akainu willfight someone like Sabo.
Could see Crocodile vs Lucci.
Rayleigh wasn't the one fighting the top rocks pirates, it was Garp and Roger. Zoro is an exceptional top commander for luffy (or will be eos), but there will be pirate captains and people out there who still rival luffy.
Luffy and his allies have to approach mariejois which is revealed to be pluton and it's firing wild beams nuking the f out of things, maybe zunisha sacrifices himself to get the pirates and allied marines on it, then the pirates pillage the holy city, on it will be people on akainus side like kizaru, etc, and also people loyal to the world government like CP0.