Why not create a government "adwords" style JS include (open sourced) that is required for sites over a certain number of users, but optional for smaller sites.

Why not create a government "adwords" style JS include (open sourced) that is required for sites over a certain number of users, but optional for smaller sites. A banner that can display government warnings or messages in an emergency. It could even use basic geolocation to only display to relevant users.