Hi Martin!
On the theory it might help to hear a similar view, I'll weigh in here again.
I'm really fascinated by your post, as it includes so many of my own concerns, particularly when you wrote...
The way I had my drops set up has another advantage - braking in all 3 positions, with the auxiliary levers on the tops. With flat bars I can only brake in the 1st position.
Like you, I use auxiliary levers on the tops of my drop 'bars, and have found them to be really helpful. I also use wide (44cm) drop 'bars, and -- yes -- I do ride most of the time atop the brake hoods. However, I also spend a surprising amount of time on the drops (hooks), particularly when going into a headwind. In my desert touring, afternoon winds regularly hold steady at 35-39mph/56-63kph, with gusts to about 45mph/72kph. I spent a lot of my time riding north along the North Sea in The Netherlands in similar winds, pedaling with my "knees inside my elbows" to present a smaller face to the wind.
I have found my wrists (hyperflexion on one, hyperextension on the other from a ballooning accident when dumped out of a gondola), elbows (tennis elbow/tendonitis), and shoulders (rotator cuff and separations from a past car accident) just don't tolerate straight 'bars well. My palms like to face each other when I extend my arms. 'Bar ends on straight 'bars would be a ready option (same position as atop brake hoods, just as you've found), but I have no drops, and no brakes on the bar-ends (also as you've found).
I pretty much have to make drop 'bars work for me, and I need braking in all three major positions. With drops, if I spend 90% of my time atop the hoods, it is also with my fingers wrapped around the lever blades. On the tops, I have my interrupter levers. On the drops, I have the full length of the regular brake levers to grab.
Thinking about Pete's (Il Padrone's) very good suggestion of H-bars...they come very close, but I would need to use them with two sets of levers. I have even considered fitting bullhorn pursuit-style 'bars in place of drops -- I'd have the tops and a wonderful forward extension wthout the weight or complication of bar-ends...but no drops, which I would miss terribly for the times when I really need/want them (wind).
The Berthoud shifter would be the best option if one shifts frequently, as many owners suggest is the case with Rohloff, thanks to its ease of use. However, I don't think the Berthoud shifter would give me the room I need for my other stuff. Unlike you, I'll be carrying a handlebar bag, and there's a lot going on near the stem (see pics here:
http://www.thorncycles.co.uk/forums/index.php?topic=3896.msg17095#msg17095 ). Also, I have some concerns about the uncoated aluminum surface in extreme heat and cold. Air temps are often around 124F/51C in the desert or down around 5F/-15 on mountain passes in shoulder seasons. Aluminum is a great conductor of both heat and cold, and I'm a little concerned the shifter could get awfully hot/cold. Maybe this is a baseless concern, but it did occur to me. Thoughts?
A bar-end position is promising and very close the familiar bar-end shifter position. The "Rohloff on T-bar" like Rual's is not much of an adjustment if you're used to downtube shifters as I am.
Still trying to decide myself...please let us know when you reach a decision; I'd love to hear which you go with, and how it works out for you.
Best,
Dan.