Making them swappable would present design challenges, but nothing is impossible if it’s a design requirement. Current EVs distribute batteries wherever they can to distribute the weight and prevent damage from collisions or debris. But if they were required to be a certain form factor and removable, cars would be designed around that. Even better, you could get away with a much shorter range, because most people want higher capacity for the occasional long trip. You might have space for two cells, and only keep one in the car most days.