Like think about it, King/Orochi could have been a Kurozumi, Lunarian hybrid that was persecuted during his childhood in Wano for being a Kurozumi and then at some point escaped only to get captured by the WG and finally be freed by Kaido.
Give him AdCoC and a variant of the dragon fruit in order to pay off the Zoro/Ryuma plot line that’s why Oda is a dumbass
King is nothing like Orochi. He was the one who offered Kaido his sword to take Orochi's head in the first place.
King has a different purpose in One Piece than just being a villain.
He followed Kaido because he was mistaken to believe Kaido was Joy Boy, and despite his loyalty to Kaido, he was still waiting for Joy Boy and Kaido knew it, even if King denied it.
I am sure his role in One Piece isn't over yet. He will end up following the right Joy Boy eventually. The Lunarian tribe was persecuted for a reason, and that reason is probably something Luffy will need, maybe an ancient weapon or some other secret that the WG is afraid of.
If you want to merge Orochi with someone to make him stronger, why not Queen? They share the same cruelty and enjoy torturing people, which King doesn't, despite being accused of it by the torture-loving pervert Queen.
Then again, Queen too has unsolved issues with the Germa, so maybe he too will appear in the next saga. Take Jack then. Jack ruined Zou just like Orochi ruined Wano. and he will not be needed after Wano ark.
if oda wanted to make zoro special he would make the shougen be super strong , or have luffy and zoro fight kaido like law and kidd fight big mom , or even give king coc and have a much higher bounty then queen but he didn't , oda sees luffy at a diffrent place then other strewhats even if its their "supposed arc".
Orochi's character is the closest and changeable with Sanji. Both are womanizer bastard who happened to be born from some evil family. Both can't die easily with Germa regen and 9 heads DF.
Germa -> evil family who occupied North Blue then made alliance with yonko Big Mom only to be backstabbed.
Kurozumi -> evil family who ruled Wano then made alliance with yonko Kaido only to be backstabbed.
Remove Orochi and Kurozumi bs, change it with Germa family ruled over Wano and made alliance with Kaido. Then we have shitty son of the family, who is planned to marry with Kaido's daughter but ultimately Kaido betrayed their alliance.
In the end, Luffy's words in Zou will also be true, as in Sanji's wife will join the crew.