I don't think it'd be that hard at all, honestly. Flag changes would be pretty uncommon and more than likely tied to events considering that ideological conflict isn't a deal in this game... you wouldn't have to have, for example, rival Communist, Fascist, Democratic, and Monarchist flags for each nation. Most nations wouldn't even need name changes, considering that the tags are pretty generic themselves (Great Britain, for example, can accomadate any sort of government type).
Changes can also be implemented gradually, like first implementing changes for Europe, and then Asia, and then the rest; just adding more of the world with each patch.
