I dont think Giani was being smart. If you want users to create other users then you should insist that they follow your rules.
Perhaps you could supply them with a creation script that they MUST use when creating users.
Something like


accept user_name prompt 'Please enter the Oracle user name: '
accept password hide prompt 'Please enter the users password: '
create user &&user_name identified by &&password;
grant create session to &&user_name;
alter user &&user_name quota 0 on user_tablespace;
alter user &&user_name default tablespace user_tablespace;
alter user &&user_name temporary tablespace temp;
exit

HTH