If they add a day/night cycle, I hope they actually use it properly.

I've played way too many games where there was a day/night cycle and it meant nothing. Other than the game being slightly more annoying to play half the time (For example, Titan Quest, where night just makes it annoying to see enemies when outside).

This would entail having actual mechanics tied to day and night respectively. Such as NPC behaviours, enemy spawns (Though this is complicated if we have their standard non-respawning enemies and the need to kill EVERYTHING to suck up all the experience points possible... Meaning having different enemies spawns means having to clear out places twice, once to kill all the daytime enemies and once to clear out all the nighttime enemies) and time sensitive interactions (Though this can be very annoying depending on how frequent and/or large the impacts are)

Another thing to consider is stuff like lighting, especially at night.

I found the general lighting behaviours in BG3 really cool. Both how torches worked, but also the ability to ignite candles and braziers in locations to provide more light (Both with interactions, as well as hitting them with fire spells), with this being even more notable for characters who lacked Darkvision and thus had worse accuracy without it. Environments looked rad with the actual mechanics of lighting.

However, such things really gimped you for actually using them. Torches suck and prohibited use of 2 handed weapons, shields and off-hand weapons. Spending spells/turns simply turning on lights was terrible. Playing the like 2 races that don't have Darkvision was also not particularly great...

That and the whole actually needing light also was not a thing. With dark places still being plenty bright enough to see properly. Heck, even the zone where it has another mechanic specifically about light... You immediately get rid of the mechanic because Isobel blessed you and then you instantly were sent to go get the Fairy who then also blesses you and makes the entire mechanic redundant.