I am surprised multiplayer is the issue. If two players are in the same party then I would expect them to mostly stick together. And if they are apart, well they both should pause and go into combat. Otherwise what's stopping the other player from running half way across the map to help out in combat while his buddy waits on his turn with frozen enemies? Or "freezing" a group of enemies as the other player freely moves around the encounter radius.
It's also curious since when I first heard of no day night cycle I just assumed it was because stealth uses shadows and if the light is not baked into the map then you will get odd calculations as the shadows move. Or likewise have shadows that are darker then they should be just to visually show clear stealth borders.
Lighting would definitely be a consideration if the game narrative or mechanics rely heavily on guaranteed lighting state. I also assumed that this played some part in the decision, although there are probably several factors.
