That's probably outside 18F's scope, as they are cost recoverable and must be hired by a federal agency. So getting that done would require convincing a federal agency to spend the money to hire 18F to build the platform. USDS could do it if it were a presidential priority, but while creating a one-time snapshot of that list would already be an incredibly huge task, actually keeping it updated would be very difficult just because of all the points of contact involved. Especially if it went down to the city council and school board level, which would certainly be useful to local communities, but really difficult to keep track of on a national level.

*I'm an 18F employee speaking in a personal capacity.