I can understand why an EV company would NOT want you to use your battery for a storage system. Cycling the battery reduces it's life. But it would be sweet to have an Emergency Power mode. At least a 15 amp 120v outlet in the back you can use for various purposes.
Japan was toying with this idea of using EVs as storage systems, but I haven't heard much about it lately. There is a spec for it.
Realistically, having a DC>AC inverter with 100 amps at 240v would be pricey. It would probably be cheaper to have a backup generator.
The Japanese spec won't have much affect on what would fly in the US, given the complexity of the electrical code and its development process. Also can we not take two 120v feeds of the DC>AC converter the car already has? I assume it's a three phase motor.
How about the ability to 'siphon' power for another EV. Now that would be utilitarian! Knock down one more advantage ICE cars still have over EVs... would definitely reduce range anxiety for EV owners as a group, too.