The Thorn Nomad can be ordered with S&S couplers, mine is one of those. There are two types of Rohloff cable types, the external type (EX box) or the internal cable type. The Nomad uses the EX box and the shift cables use outer housing for the full length.
With the EX box, the cables and EX box stay with the front half of the frame when you split the couplers.
The cables run under the bottom bracket and then under the left side chainstay. There are some cable holders on the left side chainstay that allow the cables to be hook into the holder or unhooked without tools.
In the first photo those hooks under the left chainstay are visible below the word Thorn, the photo was not taken with showing those hooks in mind so the photo is not that great for your purposes. But I think you get the idea. I have no idea if the way those cables are hooked in is patented or not.
Second photo, the cables and EX box stay with the front frame member, as does the handlebar because of my rear brake cable. This bike uses full length outer housing for the rear V brake too, I disconnected the cable from the rear brake. I have changed my Rohloff shifter placement after this photo was taken, so disregard the shifter part of this photo.
I can think of other options if you do not use full length outer housing, either that use cable splitters or cable stops on the frame. But I am sure your frame builder could think up anything that I could dream up.
Third photo is of my Raleigh Grand Prix, that bike uses the Ritchey Break Away system (competitor to S&S couplers), although the bike does not use a Rohloff you can see in the photo that there are cable splitters on the gear cables under the downtube near the coupler.
