A nice feature that could save some time on complex designs would be the addition of a "Parting Plane" tool that identifies where your model will be parted during a molding or casting operation.
Once the parting plane is created/selected, the "Parting Plane" tool will automatically draft all perpendicular features above and below the plane in the model. A dialog will allow you to specify the draft angle. Perhaps this can be incorporated in the existing "Shell" tool.