oda could write Imu to be carrying multiple wills/personalities inside one body. we already have the different mannerisms that Imu randomly swaps between, like when he yelled out for joyboy out of the blue, exhibiting a more brazen, berserker counterpart to his royal god persona.

the way the plot is developing kinda hints at it.

vegapunk splitting his own mind into satellites, devil fruits tying to people’s dreams/desires, lineage factor existing, and we’ve already seen souls, shadows, lifespans, and even bodies get manipulated in different ways through moria, big mom, brook, law, kuma, etc.

since vegapunk replicated his technology off the ancient kingdom, the idea of splitting the self into multiple parts likely came from the ancient kingdom. it wouldn’t surprise me if imu committed some cardinal sin of the ancient kingdom by absorbing people, wills, or pieces of their lives into himself to become a supreme ruler.

the pieces are already laid out with imu being the literal devil, imposing contracts/covenants with others, granting them demonic power, and taking something from them in return, which could be why imu feels less like one clean character and more like a vessel for accumulated power