As Dan has said, I converted my Sherpa to Rohloff use, and I am very happy with the way it has worked out.
I managed to do away with the need for a chain tensioner by choosing an appropriate combination of chainring and sprocket sizes, details are in the thread that Dan linked to.
I have to replace the chain more often than would be required with a tensioner fitted or with an eccentric BB, but that isn't a problem for me, I don't keep records so can't give an exact mileage per chain but I'd estimate it being around 2000 miles.
This may be an issue on multi month tours so maybe a tensioner would be better.
I didn't really like running mine with the tensioner which is why I looked into doing away with it.
You could also consider fitting an
Exzentriker to give you chain adjustment but you need a modern Hollowtech type chainset rather than a square taper BB chainset.
The chainstay torque arm is of no real consequence, it works fine, hasn't caused any issues, some people don't like the look of them.
For drop bar use, the Hubbub adapter works well, but is expensive for what it is, I like it though.
Third party alternative shifters are also available now, several options can be seen
hereOn balance, in your situation, regularly doing multi month tours I would probably go for a new Raven frame, but bear in mind that the Raven's eccentric BB can be seized when you come to try and adjust it, and might need some brute force and time to to sort it out.
Is the Rohloff worth it? Depends on your financial situation I guess. I got mine second hand, but if it was stolen I would probably replace it with a new one if I couldn't get another second hand.
I have an Alfine 8 speed on my other bike and the Rohloff is in a different league really, the Alfine is fine but I wouldn't want to go multi month tours on it although Vin Cox went round the world with his
http://www.bikeradar.com/news/article/vin-cox-sets-new-round-the-world-record-27795/