Don't confuse slow cooked bar-b-que with grilling. They are two different methods of cooking. One is done with lower heat in a covered cooker, the other is done with the coals placed much closer to the grilling surface and you do want an even coverage over the surface for that kind of cooking.
Anyone who mistakes the Cobb Cooker for a grill for quick cooking of steaks and hamburgers simply does not understand that it is not a grill and was not designed for that purpose. If you want to make a modification of adding in a higher shelf to support the coals up higher as well as using more of them then I guess you can have a double duty system for both types of cooking over coals.
I have a small barrel shaped charcoal unit for at home that is designed for slow cooked smokey flavor use. I went to the hardware store and got a piece of expanded steel mesh and made an alternative shelf for supporting the coals up higher for when I want to cook steaks. You can cut that mesh to size with a die grinder.