How about the area over by the ART ticket machines (over to the far right side, if you are facing bag check)? (Disclaimer: I haven't had a good look at this area since the Harbor bag check was expanded.) That area is open enough for the most part. The ART machines could easily be moved a bit to make room for a few benches, some ash receptacles, maybe some hedges like the ones around the picnic area. It doesn't have to be large, just clearly defined and separate so the smokers have a reasonably set apart and comfortable place to go. Most people probably aren't going to want to spend a long time there -- just have their smoke, maybe make a phone call or some texts, then get back to the fun in the parks.