@Salah WG one gap in your theory about double layered eyes: why doesn't Cavendish have double layered eyes per default to reflect someone else is inside him, but only when Hakuba comes out? As if Hakuba himself has the double layered eyes.
Also, don't forget this goat:
I already addressed this, I said Double-Layered Eyes means "Both" are looking through,
Cavendish didn't have them because Hakuba was asleep, and vice versa when They switch,
It's only when both were awake that their Eyes turned like that, and that Chapter also hints that They also have to decide who takes Control,
In other words, there might be multiple Hosts like Cavendish around the world, the OG Founders living inside them are sleeping (Think of them like Sleeper Agents), it's just that for some reason Hakuba had trouble sleeping & fusing with Cavendish, so They are in constant struggle, while Mihawk & Imu are fully awake & fused with their Hosts,
This is similar to concept of General Zombies from Thriller Bark, They also were asleep, SHs only encountered Tararan (Whose job was capturing people & ships for Moria) & Zombie Ryuma who was Strongest General Zombie by far & Zoro's Last Main Opponent of Pre-TS, while rest of Generals were waiting for Absalom to wake them up,
As for Caribou, He doesn't have Double-Layered Eyes, He instead have multiple rings similar to when Big Mom fed her Homies multiple souls, and Caribou does indeed have a DF that allows him to have near-infinite storage, and We saw him absorb people before, so Oda gave him those Eyes probably just to indicate that He fed on people multiple times,
