Let's start with a story.
When I started to work with Domino I often traveled and loved offline replicas. Files are stired in attachmebts and search did fulltext search on content, attachments and so on.
Then integration of Box, Connections or Quickr started and users began to attach only links to that system attachments. These attachments save storage, but they are not avsilable offline and the more painful thing they are not indexed in the search. Users need to search now in 3 or 4 places and do not get results in one place. I can't understand why they accepted it, but I think we need documented extension points to get all these stuff in one search box.
Searching in a widget additional to main search is always a seperate task, so I would like to avoid this. Users do not need to know where content is stored, but they need to find it.
It doesn't work for IBM products like Domino, Connections, Filenet, but should consider that customers more and more put content to the cloud. (o365, box, dropbox...)