Transporting batteries might make sense for some extremely remote locations with no grid access, but people don't commonly drive far away from the grid. As these batteries are very heavy, I would expect the handling involved to make this far more expensive than just charging on-site.
This sort of "mobile charging station" is probably much more convenient than the mechanical trouble of swapping a battery, especially with most of the EVs using the battery as a major part of the chassis and safety designs of the cars and the trade-offs of making them swappable aren't worth the loss of certain safety constraints.
A recent video on the subject of HFC tankers, in which Siemens and others are actually working to commercialize it: https://www.youtube.com/watch?v=kCmKAAh-vkE