Add a second view path (normally only "app/views" is in the list of view paths). (ref #2518)
Anything in this directory matching the app/views directory tree will override the default.
Therefore to override app/views/pages/_dashboard.html.erb create a file with this name and path: app/views/site_specific/pages/_dashboard.html.erb
Move the "override views" folder outside of views but still under apps in the Rails.root (refs #2518)
Move site_specific views folder right to Rails.root, and allow this itself to be overridden with an environment variable (refs #2518)