We are implementing the Headcount Planning for cost center.
Initially we thought that all the new head count requirements will be manually entered using the layout fixing the employee number to '99999999'. But the problem in this case is that if you have same requirement with different start date then I am not able to create the separate records for these requirements.
Please let me know if you have any other way of doing it simply.
Unless you want to set up dummy master data for employees, it may be better to look also at class of employee, # of employees in the class and rate/average salary type of scenerio.
If you actually plan to employee number it is very detailed planning then you need to cover scenrios for new hires and terminations.
Hope this helps,