We do deal with a lot of buildings that have concrete ceilings. If your ceiling is higher than 8 feet, then doing a 2-inch drop to run wiring is a good idea. This lowered ceiling will not damage the structural integrity. You could also install 3-inch-deep box beams on top of the new ceiling. These would add some architectural interest to the ceiling and give you the opportunity to add recessed adjustable low voltage fixtures, installed in the beams, to accent art and tabletops.