Suppose that WSJT-X could be modified to side-step the whole 'translate the desired rf frequency to an audio tone, send the tone out on an audio cable to the radio, where the tone is mixed in on the baseband carrier, after which the carrier and all the intermodulation artifacts are filtered out', and simply send the required rf frequency (the baseband plus tone) to the radio.? The QDX could side-step the sound card and generate the appropriate rf frequency directly (rather than detecting the appropriate frequency by means of the sound card, and then generating the frequency directly).
