More Custom Field Permissions Control

It would be very helpful to set a field as only being modifiable by certain groups / users. Currently, all techs have the same permission and can modify any non-admin field. In order to allow for say a quality approval of some sort, they would need to have a field that only quality can change to ensure validity of the entry. While the system currently tracks each user's action for traceability, this still isn't enough fidelity for our needs.