In my experience, one area in which they are quite helpful is in the instance of single-industry communities. Take a look at that scenario you were describing. In those areas of the country where they're having a lot of hardship, and those single-plant communities, the degree of freedom they have to respond to that crisis if a plant is going down is pretty limited compared to the larger communities.
It strikes me that this is where regional development agencies have knowledge, awareness, and programs where they can bring together the key players to, as you say, take a look at alternatives, whether it's tourism or something else for the community. You end up having government programs that look at the individual, and a regional agency that's able to work with the community.