A use case for this is in #1808542: Allow area handlers to override the page title when used in an empty area.. Overriding the title only really makes sense to use as an empty area handler.
Think of how views_fetch_fields would fetch handlers for a base_table etc...
We could add this 'type' to the plugin definition or the views_data. If no type/types are specified, then any area handler should be assumed E.g. Text.
Where should we put the logic to filter this? Plugin manager level? after we have got the list of definitions or data?