However, I don't think that battery swapping is the solution for private vehicles on road trips.
One of the main problems is that batteries (all types) lose a fraction of their capacity, every charge/discharge cycle. Therefore, in practice, the battery packs would be anything but standardized. Some would be good for (say) 150 miles — while others would only be good for 100 miles. That could leave a lot of drivers stranded between battery-swaping stations.
I recognize this. By standardized, I mean same size, terminal arrangement, and mounting.
The battery in my computer costs ~$100, and tells me how many times it has been cycled, and its current absolute charge (watt-hours, not percent). I would expect no less of a car battery. It might add $5 - $10 to the cost of the battery. You would only pay for the watt-hours you actually get, the price would not be the same for every battery.
The real problem with cars with only one battery is that we expect to start out with it fully charged every morning. This is the equivalent of filling your gas tank every day whether you need to or not. Having multiple batteries which are only used one at a time, with automatic switching, allows the equivalent of buying $10 worth of gas if that is all you can afford today. Not quite as subdivideable as gasoline, but a whole lot closer than one battery.