To start, they break a few Miraculous Rules: the Miraculouses themselves have no resemblance to the animal they're imitating, and their powers are closer to their Pre Cure ones, which are baking/cooking based. And the reason I have for this is that these are technically not Miraculouses and technically not kwamis.

They aren't the "Miraculous of [x]" representing a concept, they're actually fairies who desire to be heroes. As such, they're actually at odds with Kwamis and there's a bit of a feud between them - the Kwamis have always worked alongside humans and see the Fairies as reckless and violating nature's laws, while the Fairies see the Kwamis as hording all the fun and not even trying to bridge the gap between them.

I imagine akumas would start showing up in Japan in Ichigozaka, bringing out the six PreCure Miraculouses, and they'd eventually follow them back to Paris to have a showdown with Hawkmoth AND the existing heroes. While the kwamis and fairies are having it out, the humans are meeting in the middle.

Ichika uses Whipp to become Crème Fouettée (Whipped Cream), a Bunny Hero with the ability "Batter Up", which captures the enemy in a giant cake. It has the side effect of being able to extract an akuma, but it can't purify it.

Himari uses Flann to become Swirl Caramel, a Squirrel Hero with modified clacker/rope darts as a weapon and the ability "Cherry Bomb", which is pretty self explanatory.

Aoi uses Aisuu to become Glace Bleue (Blue Ice), a Lion Hero with the ability "Gelato Shake", which encases her fist in a block of ice for even more painful punchs.

Yukari uses Cookie to become Kitty Macaron, a Cat Hero with a spiked yoyo and the ability "Cat Scratch" which inflates the size of the yoyo and increases their strength, making them able to scratch through anything.

Akira uses Chocco to Chien Rouge (Red Dog), a Dog Hero with the ability "Chocolate Armose" which creates a chocolate shield.