Hi robcase0 & ab,
Leaving dangling files is definitely the worst option - diverging accounts (leaving independent user entries on single servers) create a high risk of messing up permissions later (i.e. when you centrally re-use the numeric ID for a new account, which would give the new user access to the old files).
Such processes should also take into account that there may be resources that *require* the old account to be kept (like entries in a history or in backups, which you cannot delete), hence keeping the ID available but disabling its use for logins is the typical (and proper) approach. But this still will not forfeit the necessity to re-own (or delete) those files: If they are kept because their content is needed, a new owner is to be found. If you no longer need the content... delete the files. Proper clean-up process.
Suggestion 1 to 3 will most probably help with the *technical* problem described by robcase0, but IMO that technical problem is only the consequence of an organizational problem up front. Fix that one and keep the technical problem as a reminder, in case the organizational problem wasn't fixed for all instances