BluePrint for supporting multiple regions or incidents in one server

Motivation:

Humanity Road works on more than one incident, located in different areas, each with different GIS characteristics. For instance, in one area, a complete GIS hierarchy may be available, and we can associate individual locations with the hierarchy location they fall in. In another case, we may not have hierarchy data other than the country, but perhaps we can designate a general area by a bounding polygon, or by radius around a point.

A person using the site would like to quickly select which region or incident they're working on, and have the map centered on that spot, and search results and drop-down selectors filtered for that region or incident. Selecting a region to work on should not interfere with the site's overall GIS configuration, nor the user's own personal configuration.