this
http://www.challenger.com.sg/inbox_images/4de800d910e4a2bfdc5a5597d2534d3c.jpg
it was on promo at funan challenger so i got it.
i got it cos its compact enough to fit in a medium size bag. Because of its short height, I attach a selfie stick on it to increase the height if need be. Of course a selfie stick on a tripod will still be less stable than a proper full-length tripod but usually its ok if i dont extend the stick to maximum and its not too windy
I dont think the passthrough idea would be doable in reality due to the way things are hardwired.
Thats why for your computer, if you plug in your external DAC/amp, its always the DAC/amp itself that has its own headphone jacks that you use, at least i've never before seen a device that has a headphone jack that can 'choose' whether it wants the signal to come from which DAC
Also not forgetting the B&O DAC is designed to work completely standalone without a G5 so thats also why having its own headphone jack makes sense.