Not sure your actual plan and expectations, but that's actually a big subject that you could talk in depth with with the engineer for the most economical way to get what's needed. He's seen the soil report and can advise of options. Example, my soil report when house slab was done was naturally highly expansive clay for area, so the engineer came first with a slab design at 3x's the cost finally needed.
The most sound was a floating slab and 4' of select fill, up through footers and select fill, to select fill and no footers. Since footers only reduce movement in the contraction state, in the expansive state you still have to control for upheaval. Not that this fits to your scenario, but for me, just putting footers alone, which cost a good bit, would cost a lot and do only little.
The engineer is planning for best outcome regardless of cost factor, usually, but should be open to discussing all available options.
