Edge
Kris King's Ghost
Again, whether or not Kakko grows any more has nothing to do with the issue of whether Hughes will mature into a play with sufficient size and strength to allow him to become a franchise player. Nobody is questioning KK's size. Hughes has the tools to dominate, but the knock on him is size...so whether you think he's going to reach his ceiling may likely have a lot to do with how much size and muscle he puts on.
Yeah, I tend think its not just limited to size. The way Hughes sees the ice, his hands, his ability to thread the needle with passes, etc. are some of why he is still ranked first.
The size component is seen as something that will help him apply said skills, and probably contribute to how well he is able to utilize his talents, but it's not necessarily the key point.