Tout Terrain from Peter White in NH is another excellent touring bike with rough roads in mind..
http://www.peterwhitecycles.com/tout-terrain.asp

Co Motion in Oregon will build a bike single or Tandem for your needs too..

Rohloff hubs are excellent , as a touring kit they are really trouble free, a few ml of Oil inside
and the assortment of ball and needlebearings are happy inside.

My 26" wheel bike has a 16t hub cog and a 38, or as it came with a 39 t chainring on it. good range
tandem they spec a 42 chainring with the 16 t cog as minimal

there are 10 reduction gear ratio sets in the hub, 1~7 are double reduction,

for tandem use they ,Rohloff, use a special hubshell with taller flanges to have all the spoke holes further in from the edge of the flange.

I have a set of Beckman panniers I'm not going to use anymore , made as a match for Bruce Gordon's racks, Low rider front. and custom made rain covers , would be excekllent for a tandem , 4=sized bags, accessory pockets .. PM-FS