I personally really like how the West Coast has developed. Just because a society has risen from the wasteland, and the setting in that area has evolved to Post-Post apocalypse doesn't mean that there will be a lack of problems and challenges to deal with. Before, the wasteland was filled with just people fighting for survival, but now it's wrought with Wars over Ideology, money, Xenophobia, and ambitions to conquer.
The NCR and it's surrounding territories offer the chance to truly highlight all the Lightest and Darkest parts of human nature that come with being in society; Peaceful Unification and expansion to Violent Annexation, Altruism and Charitable Organizations to Cruelty and Organized Crime. Leaders who believe the Ideals that they represent to Corrupt Politicians who taint their society. Theres a certain Comfort and seeing the NCR attempting to rebuild life to what it was like before the war, and how they built themselves on noble Ideals, but there is always this Constant fear that no matter how many great leaders, or heroes rise to protect the Republic, their potential will end up being wasted because they haven't learned anything from the War - Because in the years since Tandi's death they have conquered everything in sight and polluted their offices with the Corrupt and Incompetent - Because many who represent or lead the NCR are so quick to forget the Morals of which the Republic was founded on when it is Convenient, with some seeming to have never bothered remembering such Ideals in the first place.
Even if the NCR was not as corrupt as it is, and stood as a peaceful Utopia within the Wastes, it'd still face it's problems. Many would wage war on it for their Technology, or Resources. Others would attack it based on Ideological reason. Some might even attack it simply because they treat Mutants and Ghouls as citizens. This is just from outside threats, a growing government would harbor countless inner threats; dealing from inevitable Famine and Drought trying to take care of so many citizens at once, to the constant watch for corruption and possible Coups within it's Leadership, to ensuring the security of it's settlements from Raiders and even possible Terrorist Actions. And theres always the risk of the more distant territories wanting to split away from the NCR, and possibly spark a Civil War.
The NCR hold great potential as it stands now - Either as a rebuilt America that has learned from it's Mistakes, or as a Empire of survivors who refuse to learn from the Hellish landscape around them.
To me atleast, seeing how this Society will develop and if it can be a symbol of Redemption for America, or a monument of it's folly is vastly more interesting to me than just a a regular Post Apocalyptic Setting - Not that I'm saying a Post Apocalyptic setting isn't interesting or has no place with in Fallout, I'd just rather it be kept to other parts of America while the West Coast does this. a Post-Post Apocalypse setting is something we really don't see often, and can hold a great amount of potential for story telling.