Even custom-shaped digital screens with advertisements running along parts of plus 15 or ground-level windows would do wonders. I still can't believe we don't have any in Calgary. The one on Arris podium doesn't do justice. I'm talking about the stuff you see along retail streets, plaza's and sky bridges in Toronto, Vancouver, and other global cities, etc. Like a Lululemon, or any other global brand advertisement, playing in a video loop on a high res screen. Really adds to that big city vibe. On top of that, throw in some Asian-style neon lights on these towers, maybe even some massive lit-up vertical text banners along the sides of the towers, as seen in cities like Tokyo and Madrid, and then boom! the Core won't seem so dark and depressing to walk around post 5 pm.
Lighting can definitely make the biggest difference to anything from a run-down house to a run-down district.