Any rapid descent "in various areas of the world" would be an extreme emergency, so everything but high terrain awareness would be of secondary nature. Practical reality suggests that you would be initiating an immediate turn in the direction of the nearest airport and advise ATC accordingly. Which means, that if you're in China's RVSM airspace and your airport is to the left of track, then you wouldn't first be turning right and offset 5 miles parallel to the airway during descent.