Yeah, but since we are on topic anyways, we might as well discuss what good would it bring if the writers decided for Kirihiko to take Accel's place. The interaction between Saeko and Sonozaki members and Kirihiko would probably be pretty awesome so to speak, and Isaka can always be rewritten to kill Kirihiko's family instead, thus his strong sense of love for the city and his desire to clean it of it's monsters. Having your family killed doesn't always have to end up with the character being a super angsty jerk like how Terui was.