Could be the world's first roller coaster fully dedicated to CBeebies Land for all we know. The whole wicker man thing could have been a red herring...
On a serious note, I don't reckon there will be any sort of fancy element to this ride. I reckon the most the world's first could potentially be is something to do with the tunnel effects that TowersTimes mentioned.
We all know how both Merlin and GCI love giving weird names to elements as well.
Or unless something to do with the giant Wicker Man can be considered 'World's First'.
Merlin and GCI were beaten in 2015 on the weird element naming basis by Kentucky Kingdom, who introduced the "Corked Roll", the "Trick Track Double Up" and the "Barrel Roll Downdrop" when they announced Storm Chaser.
Merlin could also be marketing the Wicker Man theming element as "the world's first dual material statue" or something like that.
Oh god. I just thought of another world's first they could do... "the world's first SW without a world's first". I can see the marketing campaign now:
Nope. We're not hiding anything with Wicker Man, NEW for 2018 at the Alton Towers Resort. It's just a plain old wooden roller coaster. Nothing to see here. But still come and ride it, because if this thing isn't a success, the higher ups will cut our budget even more! Come on! We're desperate!
On a final serious note, I actually reckon that the world's first might not be something that Merlin is shrouding in secrecy, but something they've been dangling under our noses the whole time. I reckon
@Bert2theSpark is on to something with regards to a new ride element. I actually think that Merlin might market the lift hill as "the world's first roller coaster with an angle changing lift hill. It will change the angle you view your life through!"
EDIT: Sorry for the long post.