...And that's what I did in the script I released
Cyan already set the day length of every D'ni location to 30 hours (it doesn't do anything in game, but is a placeholder for later additions. Example: most Ages have a day length of 24 hours, the Pods of ~15 hours, Gira of 10 hours...)
I copied the script from Negilahn, which simulated daylight by simply changing the mist color and density (Gira changes the object's colors as well, and modern game engines have fully dynamic lighting, but changing the mist works really nice on old game engines). It's working by getting the Age's day length and current hour, and finding smooth transitions between fixed values (for instance, full black and high density for night). In the end I just had to find settings that feel right in D'ni, and add the pellet factor thing.
The backdrop should be more or less visible depending of the time of day, since at night the mist density is higher.
About this pellet factor: I was testing it on Complete Chronicles, and I ran in an instancing error with the pellet score. To make it short, CC doesn't have any proper place to store these points (unlike MOUL), and because the city is a shared instance, when trying to retrieve it, it took the score from another instance of the Ashemen... A "copy" of the Age you couldn't link to, and in which the pellet score was always 0.
There were other ways of doing this, but it would be too hacky to work properly online.
So the script I released simply ignores pellets, and runs like the lake was fully restored.
I added code which might work on MOUL though, it just needs to be tested.
On a side note, I'm glad this subject is being brought back. Due to the lack of response on the other topic, I was wondering whether anyone cared at all.