After reading Schopenhauer’s works, despite agreeing with most of his metaphysics, I have to object on the following: Will is not the ultimate substratum of the inner (phenomenal) world. It is itself an appearance, a different type of phenomenon, appearing on the base layer of consciousness. Consciousness seems to be the building block of existence (see On the root of existence). The will is probably similar to other invisible forces (desire, electromagnetism, gravity, etc.). But without awareness all these would be blind and meaningless.
It might be a word-game though. If Schopenhauer’s will=awareness/qualia/consciousness, then we are talking about the same thing.