Do you want something for hiking/backpacking or something to carry in your car emergency kit?
I was thinking something versatile - mainly use in conjunction with a car, but abroad, i.e. compact enough for flights and transportation to the destination.
If you are doing this in conjunction with a car, then the car is your shelter. It is superior to anything else you can carry.
Except for unusual circumstances, you are safer using the car as shelter than walking out.
+1; stay in the car. As for which bivvy, either the one I suggested in my previous post, or the slightly more expensive one suggested by AKSAR.
When you are in the car, you are out of the wind and wet: only only have to deal with the cold. This simplifies things greatly.