Its probably doable but it would be a serious dickache to make sure you dont load things weirdly.

One thought would be to have an LDR in series with the NFB resistor. I've never played with those but I know the SLO and DR use them for switching stuff. I suppose the same could be done by putting a 1M resistor in series with the NFB resistor and then bypassing it with a relay when you're not using the clean channel.