If you are talking about a peace operation, there are times when a NATO operation has advantages and times when it's a disadvantage. There are some regions of the world, like the Balkans, where you need to show a lot of force because the language of the day in the 1990s, of Milosevic and Karadzic and others, was to really respect force.
The fact that the NATO IFOR and SFOR forces were backed up by aircraft carriers in the Mediterranean made a big difference in being able to keep the conflict down. Eventually, it transitioned to a European Union mission with much less force, but there are times when you want to have the peace enforcement capability to go along with a peace initiative that the UN is leading.
I foresee that if the UN were ever to create a peacekeeping force in an area like Libya to help disarm the various militia groups, they could have some NATO backing. If it was necessary to have force behind the mission, they could call upon NATO.