You’re right on the flexibility front; nothing beats paper or non-digital media for flexibility. No limits!
What I’m wondering, though, is how to bridge some of that flexibility with connections to things like copy, “live” personas, prototypes or other inputs — these would require some kind of digital connection.
A dream, for me, is a multi-layered journey- or task-map timeline, that lives in a browser and can be updated by many people at once. Paper is where we all often start; to make it truly useful, in my view, a digital form of some type is needed. Custom diagrams (for those gorgeous posters we want on the wall) are limiting, inflexible, and not inherently multi-user.