Wadia has a license from Apple for circuitry which bypasses both the internal DAC and amp in the iPod, giving you bit perfect digital (not anlaogue) out of the LOD into the Wadia. This much is known, as the Wadia iTransport uses optical out to my DAC. It is the current, de facto standard for using the iPod as a high quality transport with bit-perfect digital out.
But if Rockbox won't pass 24/96 without downsampling (don't forget we are bypassing the iPod internal DAC), then this is all for not and won't work.