Note, BR2032 is the longer lasting (less current output) version of the CR2032. Should not need replacement for life of the machine.
Given how easily the outer casing is separated, I would not be surprised if companies like ColorWare to start offering custom color and finish services. Should be fairly easy to bead blast/anodize/paint compared to Macbook Air/Pro.
Apple's official site says the macbook has built-in stereo speakers. But I only see one speaker in the middle. Are there other speakers somewhere else?