Comment 128 for bug 93546

> in a manual way, this is what people really do, when we have the profile
> locked, we create a new profile and copy the bookmarks.

yep. Indeed thats what I do too (copy on login, copy on logout).

May I suggest using a simple redirection mechanism that simply modifies calls to open(filename) to something like...
  #1) Is there a temp copy of 'filename' yet? If not, copy over to
      tmp_profile dir.
  #2) Change open("filename") to open("tmp_profile_dir/filename")
Then, when the last instance of ff closes, move the changes to the original profile directory. No synchronization necessary, last man wins. Even this caveat would be immensely more acceptable to admins than the current state of affairs. It would be to this admin anyway. :)

The "which directory should it be" question is resolvable by either using tmp (IIRC, FF is already using LocalSettings/AppData/<whatever> under win), or by using a "virtual" disk, i.e. memory, and letting the OS figure out where to page.