@uniaka:
I really don't see why wb pirates would be there, since they are pretty much yonkou's crew without the yonkou captain. They would already be more then enough allies alone without the rest. Unless oda wants to say kaidou's crew is much better then the other yonkous since you have all those allies on top of former yonkou crew.
Nekomamushi explicitly stated that he was recruiting them to fight Kaido. Diverting them entirely to a different part of the plot and abandoning Neko's sentiment altogether would be incredibly weird storytelling-wise.
With regards to the Whitebeard Pirates' potential performance against the Beasts Pirates, the Payback War definitely showed that they're not up to snuff with a full Yonko crew. Blackbeard gave them a crushing defeat even before he established himself as a Yonko. The Whitebeard remnants likely don't have their allied crews with them especially after Weevil, while Kaido at least has the shogun and his power on his side, if not even more than that. The remnants haven't fought on a big stage for one-two years now, and considering how they've all disappeared it's quite possible, even likely, that they haven't fought at all since then.
In contrast, we're going to be confronting the Beasts Pirates at the top of their game, in home turf. Over 500 Gifters, who knows how many Pleasures, the shogun's forces, and Kaido and his upper echelon themselves. This isn't going to be like Whole Cake Island, where Big Mom's crew are starring in an arc focused more on infiltration than battle, resulting in lack of exposure, some embarrassment, and an occasional moment to shine. This isn't going to be like Marineford, where the Marines had plenty of monsters on their side to keep pace. This isn't going to be like Zou, where a powerful warrior tribe only had a slight advantage on a small contingent of Kaido's crew. This is the real deal. We haven't seen anything quite like it, but when you consider the power and reputation the Straw Hats have to go up against, ain't nothing wrong with a little overkill. That's not to mention that Kaido himself may not be one vs. one and done, given how Oda's talked about how he's thinking about the guy's defeat and knows that simple punching from Luffy won't do the trick against a guy like him. The need does not nearly come against the Beasts Pirates, but against the star of the show himself.
And it's very unlikely that tamatebako was introduced as a gift to bm since years ago only not to use it and forget about it when we get to bm's arc. Same for the creatures, must be more to them then random creatures captured by bm as her prisoners and not use them at all.
Of course the Tamatebako is going to be relevant, I firmly believe that. But Oda is known for using things in unexpected ways and the box may not be relevant in a battle scenario, which is more and more likely considering how far away it is. Not to mention that we know now that it wouldn't even affect Big Mom besides making her angry.