Woah...the Zoro fan in me cannot overlook Oda making a clear distinction on how much of an advantage blade attacks give. Through haki, blade projectiles do not have much decrease in their destructive power, so it is like having an offensive logia now. And now with this chapter, it appears to be the best defensive bushoushoku too. This attack was going to take everyone out, and even by Zoro and Kid's analysis. I honestly thought Zoro was going to be completely out of commission when he talked and dropped his third sword, but he manages to deflect the projectile and save not only the other Supernovas, but a HUGE chunk of Onigashima. We don't know where everyone has fled to, so this could have been thousands to tens of thousands dead in an instant, which shows how replaceable the Yonkou think their minions are.
Thankfully Luffy's base form has powered up quite a bit...and he's going to need it since he just took a huge attack with potentially minimal defensive busoushoku. So now Luffy and Zoro are severely damaged and fatigued and these are the strongest fighters we have. Unless Jinbei changes his plans...things need a MAJOR twist.
Yes, I read the whole chapter and the brains of the alliance (Law) came up with a great strategy and left Luffy out of the plan since he knew Luffy would just go charging in no matter what. I'm a little surprised Kid is willing to be the bait, but maybe seeing Zoro do the same makes him buy into the plan. The plan obviously works perfectly...but anyone thinking this can get rid of Big Mom is completely forgetting Kaidou can fly. He isn't stupid enough to just let her die. The Government has some sort of new power they have to team up to take on, so he knows neither of them survive the Government without the other.
This is 100% meant to be the positive glimmer of hope, but it's also why it comes without a break. Zoro is shown to be close to his absolute limit already. And all he did was a haki infused sword attack. Sure it takes a little extra stamina/energy to do the Kinemon flame cutting, but cutting larger flame attacks was nothing a few minutes ago. It is probably safe to assume that both Luffy AND Kid are in at least a similar state of damage and fatigue.
It was a perfect set up that Kid's metal, Zoro's stolen Kinemon technique, and Killer's haki blades all perfectly negated Zues, Prometheus, and Napoleon. 100% great writing by Oda and the Law fan in me enjoys his moment of his way of "gloating" with his comments to Big Mom at the end. It is perfect timing that Kaidou is distracted by Luffy, but unless Kaidou suddenly goes literally deaf (he is going to hear Law, Zeus, and in the next chapter Big Mom's screaming) she is going to be saved.
To play along with the optimistic side, the absolute best case scenario is that Luffy has enough haki to use Gear Fourth AND his base form is as strong as his comments to Kaidou about dodging are true (Kaidou actually instinctually fears the people that have legitimately damaged him => AH! So this actually makes the large number of defeats EASIER to achieve. He literally panics and cannot fight to his true potential since he cannot use all forms of haki correctly when he panics). I'm going to write a theory...and Oda just have might have gave away his plan on Kaidou's defeat.
So Kaidou will do whatever it takes to save Big Mom. He should be fastest in this hybrid form, and we already see him fly by transforming just his legs into a dragon. He does this to fly to Big Mom, and Luffy recovers enough to activate Gear Fourth and has the opportunity to just go all out while Kaidou is trying to get to Big Mom. I guess even better is that Luffy gets there the moment before Kaidou grabs Big Mom so both of them can only use defensive busoushoku and have to just eat the attacks. They in turn both take "significant damage".