I just don't get the use case of a sword that can turn into an animal. Might be useful for someone who hasn't high potency as a swordsman in the first place, but Zoro turning his swords that can decimate any opponent into a dog, what the heck is that good for.
If the Sandai ate Kaido’s fruit, the sword would most likely be able to:
-Enhance his durability without haki
-Produce flames without Zoro exerting himself
-Produce a magma like fire
-Produce lightning
-Produce tornado and wind slash without Zoro exerting himself
-Grow bigger
-move like a snake
-Produce flying nimbus
The sword would basically be able to do everything Kaido could do at the whim of Zoro.