Here's what I think will go down
- Yamato will decide she needs to go up to the roof to save Luffy
- At the same time, all the Strawhats decide the same thing. Zoro will probably be KOd and Sanji may or may not be in the same boat
- The Strawhats fight a now exhausted and demotivated Kaido in the same vein as Oars
- They do surprisingly well, but it's not enough
- Yamato comes in, meets the Strawhats for the first time, and they're able to do serious damage
- Luffy gets up in time to land the final hit
Obviously it will be different from this, but I do think Yamato will play a pivotal role. What people need to understand is that it's obvious that Yamato will be the next Strawhat at this point, but as of right now she isn't developed enough. She hasn't even met any of the crewmates.
Like, I don't see how people can think that it's more likely for Law/Kid/Zoro/Sanji to hold off Kaido instead of the character who has been blatantly spelled out as the next Strawhat and is Kaido's own flesh and blood daughter.