I agree, there is an argument for broader regional governance (whether it's the bay area, or western King County in Washington), in between the city and state level... whether through expanding existing bodies (reforming city borders) as regions develop or forming new layers of legislative change.

For example, Seattle has a problem where the urbanized area around lake washington support expanding our public transportation - but we're chained down by eastern King County, largely rural citizens who don't want or need subway lines. However, rural districts depend on taxes redistributed from urban areas to fund programs like public education... so it's not clear that breaking up the district is the answer either. Ideally we'd have some type of adaptive democracy, where each issue is regulated by the scope of people impacted by the decisions.