>> 3) Doing something about the old users' options in their `.emacs' >> files -- for instance, by moving them to the new file, or by >> ignoring multiple entries.[1] > How about binding custom-set-* (e.g. with flet) during the reading of > user-init-file, to a function which displays a warning? This could > suggest that the user move these entries to the new file. You can't tell which file it is being loaded from. If someone has changed the value of custom-file and hand loads it in .emacs they will now lose.