You need to check out the RNP-AR approaches that are the latest way to squeeze a jet down a narrow valley in IMC.
They can ONLY be flown by the "automatics". The tech crew cannot fly the aircraft accurately enough to have the ANP remain within the RNP and are just very attentive witnesses to the same ride that pax are getting down the back....until the decision to land or not to land....and if you don't land the "automatics" squeeze you through the valley back to MSA or whatever your country calls it.
The ANP has nothing to do with flying the aircraft it is purely a measure of position confidence of the navigation solution in the FMC. Flight Technical Error FTE is the measure of being able to fly the FMC track
Pucker factor 10 I reckon....but its authorised.....at least until the first contact with the granite
RNP AR approaches are so easy to fly that you can hand fly them without the flight director just using the noodle and good pitch control. The biggest problem for hand flying them in big hill areas is that they take such long time as the approach IAF can be at 10,000 feet or higher. As for the pucker factor, it is a big fat zero with great training and a good understanding of how it all works.
The thing is that the closest anyone has come to granite at this airport was flying the VOR departure!
The actual wording on our chart is that AP and AT are recommended in mountainous terrain.