The VO Camargue may be close to what you are looking for: http://velo-orange.blogspot.com/2013...e-is-here.html

I'm not sure what you mean by sub optimal tubing on the Surly LHT and Salsa Vaya; they're fine steel tubing sets just like all the other bikes you picked out. The other ones have a bit beefier steel tubing sets which may be optimal for your needs but there are, as others have pointed out, trade offs.

Given that you're not leaving until April-May, I'd look for a good quality vintage mtb with a rigid fork and then either do a drop bar conversion or go with trekking bars. You can invest in a good pair of hand built wheels and largely use the existing parts. You'll get a great stout bike that will work well for this trip at a very reasonable price.