I am fully aware of ether being the fifth element.
The issue is this element is force. It relates exactly to telekinetic, which is psionic rather than primal. Force constructs like the Shield spell are made out of ether. Likewise Eldritch Blast force damage.
In some way every power source uses ether. Psionic wields it as telekinetics. Primal might engage its sense of spiritual forces of ethereal fey and shadow.
I view the "Weave" of arcane and divine as the ether.
I thought you had posted earlier about both being weave? Why shouldn't psionic be able to reach all of it in any case? Especially if there are literary inspirations for it.
In any case, in many Asian systems, plant (to move like a tree expanding outward) is an element.
And in D&D, organizing plant as a kind of element is useful, especially because the traditional primal Druid is both plant and the four elements, but is less about telekinesis and flight.
Given the Wuxing's focus on movement and interaction, it always feels bad to me to make wood and metal work just like the other elements. Is it better to not even call those five "elements" and avoid tangling them with the classic Greek ones that they don't seem related to, and go with something like "phases" instead?
(If one is going for a big mishmash, why not a system with four elements and five phases?)