Skinner says Poulter was replaced to make The Fades more adult:
[The change] was one of the things that made it feel more sophisticated…. The guys who played those parts were absolutely brilliant, and I was really happy with what they did in the pilot. But when you looked at the series as a whole, what we wanted to do was grow up the tone of the piece. And to really be allowed, in the second half of it, to push the elements of horror, push the darkness, and the questions about what a Fade actually is.