It might be that I am just an unsophisticated FCE user, but the idea to have to launch a NLE to maintain a database of clips feels like an overkill. I understand that it is natural to do so when you are married with (or prisoner of) a particular software, but the two functions seem distinct to me. Again, I may be just an ignorant fool having too little experience with managing TB of clips.
This being said apart from one crash so far, I think Frameline 47 is THE thing. Take a look at the Annotation interface ("Notate"), which allows you to add metadata to any clip:

You can annotate different parts of the clip with a ton of information (obviously that could be a very tedious process), including predefined "Plot Stages" and load of other pro-tools I probably will have no use for, etc...
But what I really like is to have the ability to not only "filter" clips according to very sophisticated search criteria, but also to be able to get a thumbnail preview of each clip. In fact, the software even has its own editor (essentially to trim clips), if you feel like using it before exporting all this to FCP/FCE (or Avid... I did not see anything Adobe specific, but maybe an FCP XML export is good enough).
I need to experiment some more, but the fact is that the software did not have any problem ingesting my 100's of clips over several drives. The fact, though, is that when I unmount my external drives, the corresponding part of the database "disappears", so I don't have access to those clips. However, if I reconnect the drives, they instantly reappear and don't need to be re-indexed (they are if there is anything new to be found).
Worth checking in my opinion. Again, it is free...