What if scrolls had op combo trees or special-cancellable supermoves that costed 25-50% of your (max) sp to use? Dude that would be the sickest. Like Spike or RE scrolls with their combos, except with the balancing restrictions of limited SP.
If the skills/trees cost % of max sp to use, it balances itself and makes you choose between exocore skills and scroll combo paths/supers.