What FIC could do.
On slightly deeper modifications, one or two GPIO pins brought out to a connector would be ideal. Perhaps a connector next to the USB port, with connections for all the USB pins, 2 GPIO, battery VCC. I2C would be a great addition, perhaps instead of the GPIO pins.
This would be a one-time plug in to the connector by the user. The cable would then be taped or glued onto the case, to provide strain relief in case the user opens the case without care.