Ability to lock down statuses and date changes on projects but not the tasks

Our project management team sets up all of the projects in Wrike based on the approved scope documents that are created. The project plan lays out all deliverable and sub project information and dates. The project is then handed over the project lead  and they can add in whatever tasks they need to for the deliverables and subprojects.  The issue that we are having is that the team leads are changing the deliverable statuses and dates. It would be great if we had the ability to allow the leads to add tasks to the deliverables, but not be able to modify the deliverable information itself.