Shifters -- I prefer and recommend the friction option. Little adjustment needed to keep it working and functions with most any type of gearing option.

Brakes. There is certainly appeal to disc and that seems to be where bikes are headed. However, canti brakes with good brake pads -- and this is key -- work well, are easy to repair, adjust, and obtain replacement parts in areas throughout the world. If you look at the crazyguyonabike site, you can find folks who have toured thousands of miles in remote areas using canti (or v-type) brakes.

For example, here's a tourer using a bike similar to the options you mention - trekking bar, 26" wheels, rim brakes - who has toured more than 50,000 miles.

Peter Gostelow -***Adventure Cycling, Photography, Speaking, Writing | Adventure Cyclist, Speaker, Photographer, Writer

My only objection to using rim brakes is the abrasive effect on the rim. However, rims can last for many thousands of miles before needing replacement due to brake wear so in reality this is not a key issue.

P.S. As posters above noted, if you plan to use flat-type bars, the Troll is a great option. The long top tube could make it difficult to fit with drop bars. Also, have a look at thumb shifter mounts for friction shifters. Very handy.