I overheard that there's a separate train line for Peruvians to get to Machu Picchu that's cheaper and less fancy. While I understand the desire to make this national treasure more accessible to Peruvians, it seems unnecessary to create a redundant system to accomplish this goal. Why not give Peruvian a steep discount on all train tickets to Machu Picchu instead? Since the operators already ask for passports when you reserve your seats, this would be easy to implement and enforce.
One may argue that because the system is effectively fully utilized, this isn't a problem worth solving. But, by refactoring the components it will be easier to roll out changes and take advantage of economies of scale (e.g. a unified ticketing system and more train times) in the future. Why make life more complicated than it needs to be?