It's not a good idea if the assistant coach to a rookie (under pressure and with no top-flight record to speak of) is someone who was formerly a better player, with more achievements and - most importantly - possesses greater charisma and force-of-personality.
If Wane hits a sticky patch in which Wigan lose three or four games on the bounce it won't be long before someone in the media links Sculthorpe with the top spot. If it's not the media it'll be the fans. And once the connection is established in the minds of even a small group of supporters (irrespective of whether there is ANY evidence to corroborate the claim) it'll spread like wildfire and put at risk the working relationship between the two.
I'm not saying it's impossible for Wane and Scully to work together successfully. But I don't think it's where the smart money is.
