Well, this is a "surprise"! The Walliams idea itself isn't really shocking, but I just don't really feel that this is... right.
It's no secret that CCL has been a very quiet area over the past few seasons and has clearly needed work, so in some sense, this is good news as it means that this seemingly-forgotten area is getting work. But the issue is that it's another IP investment! It's of popular opinion that the original concepts (ie Nemesis) that Alton Towers do are much more enjoyable as it feels so much more unique, and therefore fun. You can't find a huge, terrain coaster themed around a million year old alien elsewhere. With an IP, you're essentially seeing something that's already been done.
Doing an IP investment- unless it's a timeless property (whether Walliams is timeless is to be argued)- is a really tricky thing to get right as it can be incredibly polarising to the audience. If you're unfamiliar with the stories going in, the attraction likely won't hit the mark, and that can feel very dissappointing.
I find this frustrating as the fate of CCL has been a hot topic for years now, but now that it's an IP, it kinda feels... pointless. From a personal stand-point, I (and I imagine many others, especially the older members) don't really have any connection with the Walliams stories, and such this prime real estate feels like a wasted oppurtunity. We can only hope that the production value of this attraction(s) means that the experience is enjoyable, regardless of guest.