The path "may" already exist. I say this because in stereo mode my understanding is the signals are converted to digital, then processed. Therefore the signal path is there. What may not exist is the ability to have the input routed to both bypass and processed at the same time. If the switching implementation were individual analog switches then it might be possible, but if it is done as an analog multiplexor, then it is doubtful. This is all pure speculation as I don't have a schematic (I wish I did).