You identified building capacity and civilian assistance for what you call nation building. I wouldn't disagree that building that capacity is important. The question would be whether NATO is the right instrument for it.
If we think about how NATO is perceived globally, I think there would be huge issues around NATO driving those kinds of civilian activities. That's why you have to look much more at regional organizations or multilateral organizations like the United Nations to actually carry out those tasks. It's because of their perceived legitimacy. In the case of regional organizations, it's that they supposedly have more knowledge about these countries in their own region. In the case of the UN, it's the supposedly magic wand that's waved that says that if it's UN, it's multilateral, and therefore it's better. That perception exists.
While nation building, as you call it—which I would prefer to call assistance for building stable institutions—is definitely something we should consider investing in, I'm not sure that I would advise doing it through the NATO alliance per se.