I have a newer player as a wizard in a converted RotRL game, and she just wants to get new spells. She went and asked an NPC wizard if he could teach her any healing spells. The magical essences and how they intersected with the traditions made for a really solid way to explain a mechanical limitation in fiction. Being able to tell a player "No, because we wizards use the mental and material essence and healing is largely of the vital essence" felt like a much more satisfying thing than just saying "it's not on your spell list."
It also made for an interesting avenue to explain multiclassing in fiction a bit, and the wizard has already started studying up on Sheylyn with the intention to take the cleric dedication at some point.
It's all just pretty neat. I hope the essences get worked into future publications, even if it is just setting books.
Thanks for sharing CM! I dig the idea as well.