Limit edit access to breakdown input / edit to a certain department - for example the props department could edit /change the props category elements and input their breakdown into the work in progress schedule. This could also go for locations dept to import scouting pictures into the Locations Category or the art department could put director plan overheads to their category or storyboard artist images would go into a storyboard category, etc.

These Dept Heads would not be able to alter the schedule itself nor edit other categories outside of their department.