Night racing has been called a gimmick, and that may well be right, it is however a gimmick with consequences.
I dont know much about Singapore nights, having never been there, but I know nights over here are cold, when I was doing endurance racing the track temperature fell away with the night quite suddenly, which caused havock with the tyres and lowering the ideal tyre pressure (which is a bit of a problem mid-race!). F1 won't have the day turning to night, but the track temperature will be much lower.
A lower track temperature reduces grip, and with the rainy season in full swing over there, there's a good chance the track will be green too. This could result in a processional race.
However what interests me is whether Bridgestone have a tyre that likes to run at very low pressures, and will all the cars and drivers cope with that?
How hot/cold is Singapore overnight?