It is an interesting question. I don't have cast in stone opinion because there is more than 1 way to skin the cat, but personally always felt ... sort of nicer, not sure what is the right word, when driving on Sea to Sky and seeing these traffic signs with both English and Coast Salish names.
I hear you - seeing Squamish names on the Sea to Sky signage is great. I especially like the Tantalus roadside viewpoint with the stories of the mountain goat hunters.
Regarding the naming of features, Mt Arrowsmith was named after Aaron Arrowsmith and his nephew, John Arrowsmith, two English cartographers.
It sounds like you have a deep knowledge of the Arrowsmith area - would you say that your knowledge of the First Nations + settler history adds to your own enjoyment of the place? Just curious - the more I learn about Squamish traditional territory, the more I feel connected to the places I have been exploring.
Many of our local south coast names came from Caps Richards during his intense survey of 1860+/- a few years. He even named Mt Garibaldi after the Italian climber. I actually visited the village of Elphinstone in Tranent, Scotland about 15 years ago where the Elphinstones family had their peerage from the 1400's. The village was named for a dark ages witch who turned her servant elves into stone, or Elph-in-stone. Every time i hike up there I'm reminded of that trip.
I personally like seeing the aboriginal names on signs and i appreciate reading what those names originally meant. Place names are meaningful.
That's rad that you visited the birthplace of the Elphinstone name. I am sure that the Sechelt and Squamish Nation both have names for Elphinstone, but I haven't seen it listed on any maps so far. I wonder if some of these places on the Sunshine Coast will ever be re-named for the original names used by the Nations in our neck of the woods?