Thanks to everyone who contributed so far!

For those who thoughtfully recommended a 4-way tire wrench, we're good on that side as where I live they are standard issue in almost every car, my wife's included.

We just switched to snow tires for the season, so I think we're good on that part too, since snow is becoming less and less intense and frequent with every year, here in my region.

So far I plan to add, based on your suggestions:

- Bottled water
- A couple energy bars with long shelf life
- A multitool with screw bits

I forgot to mention that DW drives a small hatchback, so cargo space in the trunk is an issue. This has affected some of my choices.

Take for example the wool blanket/sleeping bag dilemma. I agree with those of you who argued that a sleeping bag provides better insulation than a blanket in an emergency situation. But the thing is, I managed to keep the wool blanket in her trunk at all times because it's a multipurpose item that we actually use in many non emergency situations, like lining the bottom of the trunk when we need to load dirty items ecc.
I think I'll have a much harder time convincing my wife to keep in trunk a bulky 4 seasons sleeping bag, "just in case".

I have the feeling that the overall size of the kit will be directly proportional to the chance for said kit to be left at home or been "temporarily" moved to the garage when the need arises to load the trunk with other bulky things. From that derives my initial assumption to limit the entire kit (blanket aside) to the contents of single small bag. Something you barely notice on normal days but is always there when you need it.