I actually looked into doing the hardware so that we could support a micro-usb audio adapter like this.
It would have meant using non-standard usb configuration (connecting additional pins to the usb lines), and was too afraid of causing problems with other things.
Also, I updated the schematics fully now:
The "MAKE LOUD" jumper will connect pin 13 to the ceramic electrode on the back side of the double sided piezo electric speaker. It does increase the volume, not quite doubles the volume but something like that. #volumecontrol
tldr; no this headphone adapter won't work.