I thought that the General Comments package can be used to attach attachments (sorry!). I know that GC is not hooked into all of the applications that it should, but this seems to already have the desired (user) functionality.
On our system, GC provides the following functions:
Actions
Attach a file or picture
Attach a web link
It also (claims to) keep revisions, so I would guess it is hooked into CR already.
Maybe we should work to hook it into all of the existing packages. Just a suggestion.
Regards..