Surely it's the easiest way, and the ugliest by the results (from my point of view).
Voxels (lofts) are considered only for the fire/throw tracing, for unit<->unit "can see" estimation, and I added functionality for shaded particles of projectile coordinate estimation. There is no other usage of it. And exactly this function theoretically could be used to find out all 4 sides, and the center of the "unit shadow", to estimate slope. Or we can project multiple "particles" down to the sprite, with smallest sprites, pre-render them into "shadow" sprite and cache it. And then use it not as ordinary sprite, but as special "darkening" sprite, perhaps using Yankes' shader function.
And as I already said, it 100% will cause visual glitches during the movement, because rendering with movement now is really tricky and fancy, and it would need to be refactored before anything new added.
Volutar i just got an idea!
What if the unit's corpse FLOOROB graphic is filled with black and placed under the unit. That way the shadow always matches the unit. That's kinda what the projectile shadow seems to do. If the unit turns around the shadow is rotated too.
It will work with floorob items or corpses as well by using same system but on the graphic itself and offsetting the position 1 pixel down and 1 pixel right.
This way tanks shadows will be more or less correct.