I've just been playing BG1 and 2 again and I really think adding a night and day cycle to BG3 is massively important.
It really is night and day in terms of immersive gameplay.
Making a decision to take my thief out at night and use the opportunity to break into houses and steal from people whilst they are asleep adds so much atmosphere to the game and makes it feel real. Just like walking through the graveyard is different depending on the time of day.
Please Larian, whilst you still have the oppertunity add this to the game. It will make a huge difference.