Hi Greg,
Congratulations on the soon-to-arrive RTs! Wonderful!
I don't know if it will help of not, but in the attached pic you'll see I've routed the brake cables on my Sherpa between the Ortlieb Ultimate 5 mount and the Thorn 105mm Accessory T-bar. My bar-end shifter cable housings pass neatly behind the HB bag with this setup, which I realize is far different than the one you have in mind. I can't speak to the matter of Rohloff gearing or comfort 'bars, just hoping this might give some ideas.
If you are ride mostly in a country with left-drive cars, you may also wish to specify Left-Front braking to ease hand-signaling in traffic (otherwise, one's right hand controls the front brake, which is not ideal when the left hand is dedicated to signaling). Otherwise, I think you should have no real problems with cable routing. As an Ortlieb owner, you're already familiar with their mount and know it can be tilted a bit to allow for a bit more clearance. There is also the Ortlieb extender if needed.
I've used my Ultimate 5 with and without the Ortlieb extender on other bikes, and now on my Sherpa I placed the original mount directly on the Thorn 105mm T-bar. Functionally, they are both the same, but the T-bar provides many more options for mounting accessories; I have my Click-Stand mounted to the underside of mine, along with a bell-compass combo. To avoid drooping under full load, I found it helpful to set the mount so the empty HB bag is parallel to the head tube, allowing it to sit level when loaded. One huge advantage of the T-bar is it allows one to place the HB bag as low as possible, something that cannot be done with the Ortlieb mounted directly to the handlebars. Of course, the Thorn T-bar requires some clearance between the headset and the bottom of the stem on the steerer, and might not be possible with a very small frame.
Why do you prefer not to use an accessory T-bar? They are lightweight and rigid and offer some additional options. The T-bar collar requires 27mm (1-1/16") clearance on the steerer. On my little scale, the T-bar weighs 122.5g (just over 4.25oz) and the Ortlieb extender with an uncut long cable100g (3.5oz), so the weight is nearly a wash, given the extra functionality.
All the best,
Dan.
