While it's clear what you are trying to do (after reading through the posts), it's not clear the business requirement for not working with the sys_user table directly and dropping the EMPLOYEE table concept.
Some insight as to why you're not just working with the sys_user table may help pave the way to the correct solution.
Writing a script that runs daily will be inefficient at best, and unreasonable (system resources) at worst - depending on the size of the user base and the strategy used.
If exclusively using the sys_user table is not an option, then I would recommend redesigning the EMPLOYEE table to use reference fields pointing to the sys_user table. Then have whatever process that populates (insert update delete) the EMPLOYEE table also work on the sys_user table.
