After reading Schopenhauer’s works, despite agreeing with most of his metaphysics, I object to 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. The will might share similarities with other invisible forces (desire, electromagnetism, gravity, etc.). But without awareness, all these would be blind and meaningless.
It could be a word game, though. If Schopenhauer’s will = awareness, qualia, or consciousness, then we are talking about the same thing. But that is probably not the case, since he describes it as a blind force.