> Asking for interoperable batteries between vehicle brands is like asking for interoperable engines between vehicle brands, it's ridiculous.
Engines are interoperable to a large degree; you can switch out the engine+ecu of your car for the engine+ecu of another car more easily than you'd think because the majority of the effort will be in changes requiring an adapter plate and shaft for the transmission.
There are hurdles that make it harder (for example, auto transmissions have software that expects a particular set of engine characteristics), but by and large most engines are isolated enough from the rest of the car and the drivetrain that you don't need to worry.
Batteries are to the same degree. if you really wanted to, you could take a bunch of liquid cooled Tesla modules and fit them in a old leaf, when it’s batteries degrade.
Engines are interoperable to a large degree; you can switch out the engine+ecu of your car for the engine+ecu of another car more easily than you'd think because the majority of the effort will be in changes requiring an adapter plate and shaft for the transmission.
There are hurdles that make it harder (for example, auto transmissions have software that expects a particular set of engine characteristics), but by and large most engines are isolated enough from the rest of the car and the drivetrain that you don't need to worry.