Brazing is probably on par with welding as far as skill is concerned and Oxy Acetyline equipment is pretty common. Try finding someone who works with Al though...
I'm not saying it's 100% this or that or that it would be easy peasy but statistically speaking, far more people will be familiar with repairing steel.

It's like many other things in touring. You aren't promised to find the right tire when you need it in out of the way places but you are more apt to find a 26" wheel than a 700c, most of the time. You just play the odds with what is most likely. Someone will more likely know how to repair or replace a derailer than a Rohloff.

None of that means one is better than the other (except perhaps the rohloff).