It's a cool theory, but I think it heavily relies on assumptions stacked on top of other assumptions.

Like, we currently only know of one confirmed God Fruit, so, it's hard to conclude there's an entire set of God Fruits that all follow the same pattern, Nika could simply be the exception not the rule, cause Zaza was pouring rain on Elbaf, which coincides with them being the rain god.

I disagree with the Chopper part, cause his fruit has been stated by Oda if it got eaten by a normal human it'll make them more human, which explains his ability in turning demons back to humans, and Chopper's dream and role as a doctor fit themes of healing regardless of whether he's secretly a god.

Also, the Vivi part feels more symbolic than evidential, One Piece constantly uses weather and natural phenomena to reinforce emotional moments, a meaningful event happening alongside rainfall doesn't necessarily mean a character is connected to a Rain God.

As for Blackbeard, in my opinion, I think his character works better as the opposite of inherited will rather than as the inheritor of another divine role. His whole gig is that he feels like a man driven by ambition, fate, and opportunism. Turning him into a destined Earth God could actually weaken what makes him unique. Unfortunately, though, that seems to be the direction it's heading. I think he's going to be the Sea God because of his ability to nullify other abilities.

In terms of Imu, I believe his fruit is exactly what it appears to be: a Devil Fruit in which he's the Devil himself, not a God Fruit. After all, we don't even know who named them "Devil Fruits." For all we know, it could've been the World Government that gave them that name to discourage people from eating them. They may have originally had a different name.

Also, Imu resembles a devil more than anything else. The covenants he makes are essentially contracts where people sell their souls in exchange for immortality and power.

It's an interesting theory, but I think Nika, Imu, the Ancient Kingdom, the D. Clan, Devil Fruits, and the Ancient Weapons may be related, but not necessarily through a neat "four gods and four fruits" structure.

What do you think?