One point to make is that even with a modular battery design you probably wouldn’t want to make short term battery changes to save weight for less range of not needed. The batteries are a lot of the cars weight and a lot of systems in the car are designed for a specific weight. It would be a lot harder to design a suspension system that could handle the weight range of everything from a 40 mile battery with single rider commuter to 350 mile battery with a family of five and luggage in the trunk.