Hi Dave!
I regularly ride all 15 bikes currently in my stable, including my 2012 Nomad Mk 2. I've owned a Sherpa Mk2 and have extensively ridden a Thorn Raven Tour, giving me some perspective on these bikes both on their own merits and compared to others.
I am thoroughly pleased with my Nomad and use it primarily for true expedition touring where I must carry a lot of food and water for sustained self-supported touring in areas where there aren't stores. It is also my best rough-road bike for logging roads and cross-country riding on singletrack and no-track. I'm very pleased with it overall and find it also good for up to 200km day rides unladen, though the rides are often that short because I am tempted off main roads by much slower rough tracks I would pass by on my lighter, less rugged bikes.
In off-forum correspondence I am often asked the same core question you are asking: Nomad or some other Thorn, like a Raven (or when it was being produced, the Raven Tour). The Nomad is a "lot" of bike, built very sturdy and designed ideally for carrying heavy loads reliably on questionable roads. To do so, the frame is stiff and robust and necessarily heavy or heavier than bikes with lesser capacity and capability. This also means the unladen ride can be stiff, too stiff for my tastes on rough logging roads without substituting a suspension seatpost, which fully addressed the problem and made it an ideal mount for all surfaces in my use (the bike has always ridden well and comfortably when fully laden). The robust frame also adds weight so an assembled Nomad with comparable components will weigh more than, say, a Raven -- outfitted the way I like, mine weighs 20kg dry.
I'd say of you want or need a healthy margin for carrying the heaviest of loads and/or on the most rugged of roads and might someday need or wish to fit a suspension fork, then the Nomad is an ideal choice -- I've never regretted mine and love it dearly. If, however, you want a bike that feels more lively and is lighter for unladen use and might even be a better general-use all-rounder, then the Raven could well be a better choice when considering more reasonable loads. Certainly, I found an older Raven Tour (more robust than the current Raven) kindly loaned to me by Forum member AndyBG to be ideal for a very long European tour that included truly awful roads in Bulgaria and Eastern Europe. The bike did very well for me and I could not have asked for more in those circumstances, but would have found it sorely lacking in load capacity for the kind of long self-supported tours I make in America's Great Basin deserts and through the mountain passes and forests I must travel to reach the desert.
I suppose each person builds their bikes in their own image of what is "ideal" for their needs. With that in mind, you may wish to look at my "Danneaux's Nomad" gallery for my approach to building a Nomad:
http://thorncyclesforum.co.uk/index.php?topic=4523.0As for your other questions...
• I have found Thorn's front and rear racks to be very satisfactory, and I am extremely fussy about having stable, sturdy racks. I also own Tubus Logo Evo and Cargo Evo rear racks and one Duo and two Tara front racks. They are also good and stable, but at the extremes, I have not found them to be a sturdy as Thorn's offerings, which are a little heavier and seem to have thicker tubing and certainly more robust mounting points and hardware. In testing and use, I have found both Thorn and these Tubus racks to be more resistant to lateral movement than either of my Surly front or rear Nice racks.
• I have found my SON dynohubs and various chargers to be well worth the cost and use them often for charging, leaving the lights operating in daytime for greater visibility to oncoming and following traffic on day rides and at night. As for chargers, they allow greater independence from mains power and allow me to recharge and power my phone, gps, and spare Eneloop batteries. I've had good luck with B&M e-Werk, Tout Terrain "The Plug" chargers in various iterations, and most recently, my two Cycle2Charge units. All have worked well and reliably for me in some pretty severe conditions without fail.
• I readily agree tires are a big factor in bike feel, handling, and how it can be tuned. I prefer 2.0in Schwalbe Duremes for all-round use of the type described above, but others are also good. I briefly fitted some 26 x 1.5in Bontrager road slicks to the Nomad and found they provided a fun but harsher ride and really weren't any faster than the fatter Duremes. Given the cost of the Rohloff and SON hubs, I'd be inclined to fit the rims and spokes needed for heaviest/harshest use and then play with tires rather than build up two sets of wheels. Better to go with a lighter bike for those times when you want to go fast unladen -- horses for courses, which explains why I have a number of bikes.
If you do have Thorn/SJS Cycles build up your Nomad with lighter rims, then you could always replace them with a heavier-duty model later if need warrants.
Best,
Dan.
