I don’t know about Campy but if a Rohloff shifter cable set is not available, instead of Rohloff’s own shifter cable sets you can use conventional 1.1mm stainless steel  GEAR inner cable running in standard 5mm dia  BRAKE cable housing. I’ve always used Rohloff cables and their own cable end caps which I think have some kind of sealing arrangement inside but I dare say standard 5mm brake cable outers end stops would work.

I use gold-coloured metal valve caps. They make it easier to both see where the valve is on the wheel and where the cap is when I've put it on the ground.

My long day-into-night randonneur rides mean I often include a wearable LED headlight in my kit so I can effect repairs in what otherwise would be moonlight or dark of night.

After one 02:00 puncture where I spent more time looking for my presta valve cap than I did repairing the puncture, I wrapped a thin strip of self-adhesive reflective tape around each cap and never had to hunt again as they showed brightly in the sweep of my light. Did the same for my black tire levers and put an additional spot on my patch kit.

Sure made life easier!

Best, Dan.

How much motor traffic did you meet on those roads, and how courteous were the drivers?

Once I was away from the larger urban areas, I was mostly able to plot a course that avoided the busier roads. There are a lot of roads to choose from. Sometimes it was a balancing act, because getting off the main highway meant meandering through a maze of back alleys with stop signs every block, or climbing a hundred meters up a 20% slope to avoid the highway following the river valley. A lot of times though, even on the main road there would only be a one car passing every couple of minutes. I would say in 26 days of riding there were only about 30km where I thought to myself “this sucks”. 

The level of courtesy shown by Japanese drivers is almost incomprehensible to someone coming from North America. On the few occasions that my route planning was less than stellar and I found myself on the side of a busy, shoulderless highway, I was never passed “too close for comfort”. Most cars were small enough to pass without crossing the centre line, although most moved over when possible. Every one of the trucks would wait patiently for a break in oncoming traffic to give me a wide berth, even when I was grinding uphill at 6km/h. Leaving Kagoshima, on a particularly busy stretch, trucks would be stuck behind me for a minute or more before there was a break, or I could find a place to pull off and let them pass. No horns, no crowding, no drama, just patiently waiting. I always gave them a thank you wave, which was always returned with a friendly tap of the horn.

Japan also has a 60km/h highway speed limit everywhere but on limited access expressways where bikes are forbidden. Even though this seems to be a “guideline” rather than a rule, it meant even on highways most vehicles were going 70ish, compared to here in Canada and USA where everyone on two lane highways passes at 100 to 120 without slowing down or moving over.

I'm sticking with 700C for now.
I like mudguards, but I also like riding on muddy trails.
As you say, the two don't always mix well.
I may try some 'gravel' guards and see if that works as a compromise.