In games that include day/night cycles, I often end up feeling that the nights are way too long. So much of the charm and flavour of how an area looks gets lost when the screen goes "no, it's night now. You can't see".
Same for me, actually, but there's nothing wrong with having short nights and long days in Summer time. And night has charm and flavor too, albeit of a different kind and in smaller doses.
Personally I'm still hoping they make "Night & Day" the main theme of D:OS 3. That, and the passage of time. If it's too complicated as a stretch goal and too complex to include at all when there's so much else going on... then focus on it completely and give it the attention it deserves.
It could be tightly integrated with the main story, some obscure and all-encompassing light and darkness duality problem. Or, more down to earth, something to do with the sun, the moon, and the source. Divinity already has all the elements, but no real light and dark magic (curious, given its name). There could be a whole gameplay system behind the night and the day, although of course there's always the question of whether it would be enjoyable. Waiting around is boring and dark towns are bleak, so they need to be made fun in other ways during those hours.
Dreams are one thing that could be explored at night, as are nightmares or course. What if they were corporeal? If you could enter them at night and return with physical manifestations?
Or how about this then: Zelda - A Link to the Past had a whole world to explore, which featured a "dark" parallel world that you could switch to at will via a magic mirror. It opened up all kinds of interesting possibilities. Would something like this not work just fine in D:OS? Have a second teleporter pyramid pair, one that doesn't teleport through space, but through time (or through dimensions). Maybe exactly 12 hours back and forth. Invent reasons for stuff to prevent time paradoxes. ... or, uh, perhaps it would be easier to just do dark and light mirror worlds like in Zelda, or simply have a phase-shifted continuum on top of the real world. The latter would defeat the purpose of having a day/night cycle though...
Anyway, there are lots of (explored and) unexplored gameplay opportunities with night and day, on top of all the usual benefits.
