I'd like to see day and night enabled again. It adds a lot of ambiance (atmosphere) to the game.
But not only that it also changes game-play, when it's dark characters become harder to spot especially invisible ones.
Same for weather, rain makes it slightly harder to spot invisibles thus weather/day/night change gameplay and makes the game dynamic.
As such weather should no longer be allowed to be disabled.
I do foresee complaining about rain, but to be honest: you've been spoiled that you can disable rain.
Also the day/night cycle makes candles more useful again and gives the light spell from the mage a purpose again.