Ability to remove resources from tasks/SOs

Often a task or SO gets re-assigned after someone has logged hours on it. Once those hours are approved, they are permanently associated as a resource despite no longer being involved. This is especially problematic if the task spans across days/weeks. Resources should be able added/removed freely while the timesheets remain. That will make the calendar more accurate and remove people who no longer need to be involved. Especially if they have been let go or they quit.