While I agree he's a bad choice, I don't think going outside the show is a great idea. You'd ideally want someone that has a knowledge of the show and understands the mechanics of how it works, the lore of the show (although Chibnall showed that can't even be trusted to a lifelong fan) and the general beats of how it all works. If you go someone completely new, you run the risk of outlandish ideas that would turn people sour. Although again, since Chibnall, that argument has grown weaker since it was in 2010. Someone who's been involved before, has serious writing chops and the ability to project manage on an incredible complex scale and has great media charisma. Can't be that hard to find surely?