Stereo AB Switch With Remote

[stephentoback]

I'd like to build a "nano" pedal sized AB Box that has a stereo input and a mono output. No footswitch. I'd like it to have a control input so that my Line 6 HX can switch between the left and right inputs using it's amp switch mode. I currently have a Champion AB box that does this (running it in reverse) but I have to use a stereo splitter to plug in both sides. I have a 6/12 doubleneck acoustic that is wired in stereo - 6 to left and 12 to right.

I've found plenty of AB box designs but I haven't found one that can switch with a remote signal input.