Anyways, no. A empty light/darkness system would take me out of my immersion. It was useless in BG1+2.
Unless you implement an actual day and not jsut the framework, the discrepancies would be even more visiable. The static world is a bit off, a mostly static world with just some paint over it will be even worse.
I do not understand your dislike for origins. I had no use for them, and still don't, but all they do is to allow you to play a companion instead. Since the character exist regardless of him or her being a playable character, I also rather doubt it is that expensive to create them.
And I do not see how they damage immersion, if you see the problem there, please tell me. (Since it is a bit offtopic, just send me your opinion or links to your statements instead, if you prefer..)
A day system is already implemented, the issue is that it is completely disconnected from the actual time flow in the game. Go to the dialogue tab in the journal window and you will see that the recorded dialogues are split in days. My current run is on day 3, despite the fact that the party went through something like 10+ rests already, and each rests implies sleeping through the night. So for me this is an immersion problem, because the dialogues are an important part of the narrative, and the way the journal tracks them isn't reflecting what happened in the game. By comparison, the day & night system was used in BG2 to build the narrative, because certain events (vampire and thieves guild war) would happen only at night.
Also, the actual time flow in BG3 is just weird. For example, you can trigger the grove gate fight with a summon, and then get rid of the summon. The fight will then proceed without the party in real time, while you can go adventuring. At some point when my party returned to the gate the bodies of the fallen were gone. Yet in another example, when I've triggered the druids - tiefling fights by stealing the idol, the fight would start but never proceed unless the party joined in. Both the druids and tieflings would just stand there in fighting poses.
