Trouble with goat milk is it tastes like the goat pissed in the milk. I like goats cheese and butter, but not the milk. One of the reasons for 2 cows is that milk is a good trade-able commodity. And as much as we fantasize about being completely self sufficient, its small village sized communities that stand the greatest chance of surviving a breakdown of society.
I hear you on the trade-ability of milk. Splendid thinking. As to goats' milk, how many times have you tried it? And do you know the circumstances surrounding its production? If you have a buck present with the does, the milk can have a bad taste/smell, but as long as there is no buck on site, the milk should taste fine. My wife last year did some taste-testing with some folks. One person picked the store-bought (cow) milk for the goat's milk. We had a friend's buck for a couple of months last year, and during that time, I could taste a "wang" to the milk, but it wasn't too bad. For this reason, we take our does to another owner for breeding. It got to where I could smell that buck all the way to the house, and they were kept 100 yards away in the barn. I compare the goats to deer. I've cleaned dozens of does and dozens of bucks. I can tell the gender by the smell unless it's early on in the season. Goats are the same way....the does have no smell at all compared to the bucks.
Another trick to good-tasting goat milk is to cool it ASAP. We pour it from the pail into a jar and either put it in the freezer for an hour, or pour it into a glass jar and place that into a larger bowl full of ice. Goat milk has hyper-active enzymes that will cause it to spoil more quickly than cows' milk. Still, for the maintenance of goats, as well as the near-perfect amount they yield, I prefer them to cows. I would raise a young one for butchering, but my wife and daughters wouldn't hear of it.
Our Nubian had triplets last year. We had her and the Alpine bred this year. Hoping for at least four kids between the two of them.
True self-sufficiency, is as you say, is a fantasy. One might survive, but that is all they would do. Still, every step taken is a help if/when catastrophe strikes.