LDAP: change internal username on prodution


I have the following problem: I added an ldap connection to the server, but didn’t touch the “internal username” setting in the expert tab. So now all users have the generated internal name like 00562af-5656b-…

I could change it to something more useful like the ldap uid, but this works only for new users. I there a possibility to migrate the old users? I could

  1. change the setting,
  2. backup the ldap,
  3. delete all ldap users,
  4. restore the ldap backup.

That would get me the good “internal name” for all users, but I guess that I would lose all the other information (files, shares) of the users. Is there a way to backup that information and restore it to it to the “new” user?