It'd be cool to use Neighborhoods to sort of expand cities into spilling outside of the city proper.
Scatterings of houses outside the walls of Stormwind, a larger clump in Goldshire. Same for Org and Razor Hill. Make those capital areas really, really, feel like capital, especially now that there's a legitimate reason for there to be a lot of houses there. They can change models and decoration upon phasing in, etc.