David Gaider: If I didn't have a day/night cycle to work with, I wouldn't include a plot where you would have to be in the same area in both time frames. That does not mean, however, that there aren't plenty of plots or even ways to work around it.

Consider this:

You get your quest to rob a particular mansion at night. You proceed to that part of the city to perform the quest (perhaps a new area that opens up). Have a cutscene of the sun going down, and you're now in the new area that includes the mansion and it is night-time. You perform the mission inside that area entirely and it remains night throughout (as it should). When you leave, you have a transition cutscene and you're back at the regular day-time city area(s).

Does that strike you as being limiting in any fashion, story-wise? The only difference we're talking about here is having a transition from a day appearance to a night appearance in the same area. Heck, if we really wanted to and needed it for the plot, we could even include two versions of the same area... one day, one night... and use either as necessary for whichever plot required it. The only difference is that you would never be standing in that area and have it go from one to the other.​