I agree Jo is holding the franchise back, but I also don't think they can go forward without her. She needs to take, maybe not a back seat, but at least the passenger seat, with this franchise. Her pace leaves a lot to be desired. I'd like to see her develop the overarching concepts, characters and settings for 3-4 series, but leave the actual writing of storylines to others. This way, it's still her creation, but other creatives are responsible for delivering the goods.
She's still going to have a good grasp of the world itself, so she should also be new writing books. That's her strength. Leave the TV series and films to others who are good at it.