Well that would be easily remedied. Every tier have apprentice(automatic), adept(solo mobs), adept 3(crafted) master(heroic drop), grandmaster(character selection), and add a new tier of epic dropped spells. Would be pretty similar to the gear progression we have currently with the new spell tier being the fabled equivalent. Yes I know fabled gear drops from heroic instances and I have always been against that, I think each tier should have it's own unique level of rewards.
I see this as a way to create a new teir of rare and prestigious spells that we used to have with masters before SOE watered them down. Don't really see any drawbacks outside of people wanting top tier stuff without actually doing the top tier. To those people I would say put in the work, reap the rewards.