I don't see what's wrong with the idea of Borg technology being sentient without an organic component. Isn't that the whole idea behind the Borg, that the overarching collective program enslaves the minds of the living beings it assimilates? And the walls gaining the ability to absorb matter into them is merely an extrapolation from the Borg's use of nanotechnology. If it's assumed that all their technology is assembled from nanites, then it should have the ability to transform or to deconstruct matter on a molecular level. It's basically your classic "gray goo" nanotech scenario. One may quibble about the extremes to which it was taken in Before Dishonor, but the underlying concept is sound.