Eric,
If you don't already have a Rohloff, strongly consider getting the "EX" model with the external cable box. This version uses two standard gear cables that run from the twist shifter to the cable box. Inside the cable box, the cables wrap around a pulley wheel, which in turn drives gear wheels to change gear.
I would not want to replace one of these gear cables on the side of a mountain in the pouring rain either, as they have to be cut to a precise length - I would suggest measuring this distance on your chainstay and making a couple of marks to allow you to do this quickly. However, the other nice thing about the cable box is that if a cable were to break, you can just detach it from the hub and use an 8mm spanner to select gears in extremis.
The only issue I've had with mine in 4 years of (ab)use is that the knurled bolt on my vintage of the cable box, which is used as a semi-quick-release to detach the cable box from the hub when you're removing the wheel, has a tendency to work loose when done up finger tight. I just check it occasionally and all is fine. Newer ones have a slot to allow you to use a coin or screwdriver to tighten or loosen it. Given the choice, I would prefer the knurled section to be a larger diameter, to allow you to fasten it tighter while still allowing you to remove it without tools of any sort.
-- John
