Even if we assume battery size/shape standardization, this would move the baterry liability from the car owner to the battery pack vendor, since they would have to maintain the batteries in circulation (introduce new ones, retire old ones) etc. This would require crazy high locked capital and it would cause the cost to be prohibitively high for a casual weekly swap.

I wouldn't trust a high voltage battery pack that is structurally important to the chassis to the minimum wage equivalent of an oil place technician with the uuga-duuga impact gun.