Universal batteries would be bad, but standardized batteries would be great. If a battery has certain dimensions and gives a certain output, and can regulate itself as to charge and discharge, it doesn't matter what chemistry it uses or internal cells it has. We have had D, C, B, A, AA, AAA, etc., for years and manufacturers got along just fine within those specs. Removable batteries are already a thing with Gogoro scooters in Taiwan and I think at least one car brand in China.