I write this pretty much every time this topic comes up.
The kiwis have a pretty similar situation with their ski resorts. High, above tree-line resorts with no local accommodation, so everyone has to drive up every day. Their access roads are worse than the Cairngorm one by a factor of several orders of magnitude (think steep, unsealed, massive ruts and bombholes, no barriers, death-drops to the side). The weather is pretty similar.
They have a very simple policy when it snows – no chains, no access. There is an enterprising chap at the bottom of the hill renting/selling chains. Simples.
France is pretty much the same too – no access beyond this point unless your vehicle is properly equipped.