I like you're thinking here, makes sense on a lot of levels. No one can deny the cultural impact on market share, rivalries, general fit. Make no mistake, NC is a southern state.
The one solution here is that BiG goes big in NC and brings aboard Duke. If we look at the ACC today, the heart of that conference is Duke/UNC as a duo. It's one of the best rivalries in all of sports and would add an intense rivalry. Meanwhile they gain an Ivy level academic. From a pure marketing perspective, it's a no brainer. If you've ever been down to Charlotte or Raleigh, what you realize quickly is that it feels like half the population are transplants from the NE and the Midwest. While still very southern, it's evolving. It does feel like a stretch today, but Delany works with a crystal ball. This would buffer the blow of UNC adjusting to a starkly differing conference culture while offering UNC a nice chip to boot.
The SEC and the BiG would not be looking to create a similar product in that state - NC is still a hoops first state, tobacco road. While an NC St/SEC could certainly create some nice buzz, unlikely that it would trump the romance of what UNC/Duke means to the people of NC.
I like the optimism, but too much to gain. Not a bad recruiting basin either.
http://footballrecruiting.rivals.com/content.asp?CID=1239398