Can I install caliper or cantilever brakes on a frame and set of wheels designed for disc brakes?
You would need a new fork in the front to add v-brake bosses and the frame does not support this either. I don't think it's worth the effort on this bike. It's sure not going to be easy without replacing both fork and frame.

I think for your situation, what may be a better solution is to switch to Mechanical Disc Brakes. They are much more field serviceable than hydraulics.  I'm going to recommend avid BB7 brakes since they are easy to adjust (you can adjust pad position on either side of the brake) and very easy to find parts for (most shops are going to have pads).