Again, it depends what you mean when you say "acoustic" (why do I feel like Bill Clinton when I say that?). Assuming I remember it correctly, the Judy Collins cover of In My Life is an arrangement for multiple instruments; not a "one guitar and voice" arrangement. In fact, I believe that most of the instruments on the Beatles' original rendition are "acoustic," too.

The key here is not the "acousticity" of the instruments. The key is whether a solo performer can do justice to a song that was originally recorded in a more fully orchestrated version. I still say that one can do this, provided one has the skils, and the willingness to tamper substantially with the arrangement.