Just to make this more involved I’m also looking for some advice as to the value of various upgrades offered by Thorn when speccing the build. In particular:
Are there significant benefits to be had from spending £200 on XTR brakes?
Shoud I get XT, or even Phil Wood front hubs?
Should I be thinking of ordering better chainset/crank/bottom bracket combinations than those offered as standard?
I know this is a long post with many questions and lots of scope for subjectivity, so thanks for your patience and I look forward to some valuable advice and opinion.
I cannot really comment on the nomad but I know it is specifically designed for this kind of journey, especially if you are carrying very
large loads. However the tour is more than capable of shifting a large cargo. You need to ride both at SJS to decide whether the 'slightly' lighter build of the tour is preferable to the bomb-proof build of the nomad.
Whichever you go for the important part will be the wheels, get the strongest you can. I'd recommend the carbon coated rims. In answer to your other questions: No, I don't think XTR brakes offer significant advantages over XT, certainly not worth £200 IMO. I have XTR shifters and avid ultimate brakes and they work very well but in hindsight this was an extravagance.
I don't think you'll better the standard BB and crank set up for your trip. There are lighter combo's but these are not really relevant to you, whereas strength and simplicity are.
There are two current blogs you might find relevant:http://www.crazyguyonabike.com/doc/page/?o=RrzKj&page_id=143297&v=9ahttp://takeonafrica.com/