I've noticed one small flaw with the prologue. It's probably not a good idea for it to be set 200 years after the war since everything is based on the way things are in the anime currently, 200 years in the future things would look pretty different. So imho a setting based 200 years into the future would be more appropriate for a game that is more loosely based on the manga/anime as opposed to being directly influenced by it and it's current state/design of surroundings.