Knowing the two pilots involved I am not convinced that they would have ignored any reasonable warnings with regard to terrain or equipment.
looking at the information available, the question that comes to mind is how cold soaked the airframe was before it entered cold visible moisture laden air.
The next question is how this affected a non deiced machine for both control and instrument readings.
The other issue is the unknown situation re the electrical system based on an image of the voltage light.
Again, the aircraft had a engineer on board who knew the machine and its system. Knowing the length and type of flight I suggest it is unlikely that the flight would have been continued if in fact there was an actual charging issue.
The initial accident report is both comprehensive and thorough, but I feel some ' indication ' is required as to the possibility of icing issues being a factor. Of course there is no actual evidence available to confirm or otherwise, but with such a common American airframe there must be information available as to the effects of the onset of icing in a situation where it is not possible to quickly enter a warmer region.