I think the interesting question is this: Luffy has beaten 3 Shichibukai, but each clearly was stronger than the last with their abilities. There is no set standard of power within the Shichibukai. Mihawk is likely one of the strongest characters in the series. Weevil is allegedly similar to prime whitebeard in strength. And then Buggy exists lol.
While we can certainly treat BB and Shanks the same way, considering the former will probably grow immensely before the EoS and Shanks is a complete enigma (who knows how strong he really is), we can't for BM and Kaido. They are essentially equal in many ways and have been treated as such. They fought for days with practically no damage it seems and in 40 years they can't best each other.
So its interesting to me if BM doesn't actually go down in Wano. But how do you beat one Yonko without downplaying the other? How is that even possible?
But then you think about O-Lin. I have a big feeling Luffy is gonna knock her back into that state, and doing so will remove her as a threat from the arc at some point. As much as people hate it, its a way to not downplay Kaido while also showing that Luffy is strong enough to take him on eventually. It also doesn't mean her crew can't go down this arc either. In fact, I see most of the BMP losing here, and many of them reforming under O-Lin's personality. This way the Elbaf plotline could potentially still happen, but she'd be more an ally than villain.