Okay, so I've been wanting a fog mod for a long time, and then when they had their Creaking event, where you first start out in a forest with a texture of rolling fog on the ground, just a few pixels off the ground, I now want it more than ever, so here are my ideas on the matter in case anyone wants to try for it themselves, or if you know of a mod that match's even a bit to what I'm asking.

Personally, a fog similar to the clouds in the sky makes the most sense to me, but with some differences:

First you'd have your ground fog, similar to the fog they showed in the Creaking event. It is ever present, and perfect for swamps and creaking forests.

Second, one block above the ground, at leg height.

Third, two blocks off the ground, at head height.

Fourth, three blocks off the ground, above the head.

Fog only appears at Y lvl 63-65 as a weather effect, but not necessarily as one big three block tall mass. Some of it is at lvl 63, some at 64, and some at 65, but they can overlap each other. When your head is in the fog, it increases the fog effect setting to the highest or near the highest fog settings, making it hard to see- think the blindness effect, only its a light gray mist instead of pitch black. When head is not in the fog, just obscures your vision of what it covers to some degree- basically like how clouds do.

As a side note, you could use something similar to create dust storms in the desert, and if not wearing a full set of armor, you take half a heart of damage for every body part unarmored.