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.
I think this makes a lot of sense. The concept is also part of the VOY episode, "Drone", during which the Doctor's mobile emitter is hijacked by nanoprobes. Before Dishonor just runs with these concepts ad absurdum.
If that were the case, why bother with the organic component at all? Seems like it is more of a problem than a help. And I didn't think that the Queen's little naked head in "First Contact" offered much of a threat without the organic component--it was probably screaming for a body to restore it.
In "Drone," those were nanoprobes from the future, where the Borg may very well have evolved into more mechanical beings.