Can I install caliper or cantilever brakes on a frame and set of wheels designed for disc brakes? I have a 2008 Giant XTC 01 that came with disc brakes. Those brakes have been difficult to service throughout my time with the bike, now the pads on the back are worn out the fluid lines on the front has ruptured. As such, I'm ready to consider replacing the disc brakes with more easily serviced calipers or cantilevers. The problem is, I'm not sure whether my frame and wheels will support this style of brake. Attached are images of the fork, wheels, and frame.
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).