It's a great theory specially because Kishi loves symbolism.
We really have no idea about wtf Zetsu really is and what all of his abilities are. We know he has something to do with Hashirama. Kishi showed us what the White Zetsu was capable of (cloning people down to their chakra by just touching them, coming back to life, transporting super fast from one location to another through the ground, interacting with the Black Zetsu through "roots", chakra absorbtion, etc) but what do we know about the Black Zetsu?
Black Zetsu is the mysterious one. He knew what Itachi's legendary weapons were. He was the closest one to Tobi throughout Akatsuki. He knew about the Moon's Eye plan, etc. He claimed he was the land itself. Atm, he's fighting the Mizukage and her whole group by himself. While the White Zetsu might be a weak fighter, Tobi did not state anything about the Black Zetsu.
Your symbolism theory is good and all but Bee is not just the Bee by name, he has an Octopus/ Ox inside of him

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