Concept/Comic Art Functionality
I currently use a hybrid tablet for a webcomic, but I love doing my linework on a more traditional medium like bristol board. Usually, I scan the physical copy in after adding ink and erasing my pencil work, and it is definitely the clumsiest part of the whole process.
I would love to see Rocketbook have the sort of non-photo blue functionality that you used to get with old photostat machines - that is to say, using a blue pen on the page would be invisible after scanning. It would give users the ability to make a pencil-like sketch in the lighter blue, and ink overtop in black - but only the black would be visible post-scan. That kind of functionality would be hugely useful to someone like me and I imagine creative types in other fields as well.