MC:
He may be reincarnated or not, he may also know the plot of the anime or not, I don't really mind. And I would prefer his Kagune to be a Rinkaku, but if you want another or all of them at the same time, you can do it.
Plot:
It would be really interesting if the MC was a villain at the beginning, not the homicidal type, but someone who steals money and avoids hurting innocent people.
He would join the League of Villains and abandon it after the failed USJ attack. I think it would be interesting if he was arrested at some point to have an arc of him in prison, then escaping while causing a massacre.
You can honestly ignore everything I said and just write a fanfic about an MC with Ghoul powers. I don't even believe anyone will listen to me.
Ending:
I guess it will be the same old thing: kill All for One and live happily ever after.
Extra:
The MC will wear a trench coat and a mask to hide his identity. He won't feed on human flesh, but I'd like him to do vigilante work by killing homicidal villains.