Besides the typical minor tweaks to the layout, I made a couple of significant adjustments to the board over the weekend. For one thing, I corrected the values of the pull-up resistors from 1M to 10k. I also moved the location of the Clip LED to a spot next to the TRRS plug, where both could be visible from the same end of the enclosure (if any).
Weaving the signal wire for the latter change has me thinking more and more that rotating the FV-1 90 degrees clockwise might be worth the effort after all.
With the opening up of space near the Arduino RX/TX pins, I'm also back to contemplating an I2S interface for this board; I'm just not sure yet how to do it.