Good ideas
I might be able to add that without any problems
To your question about the black footprint. Its not possible to have Decals with Displacement Maps, so they currently only got Normal Maps and Opacity in Sand/Mud. It just might look black at first, but its actually just the shadows created by the normal map, where I am also quite unsure why it sometimes looks darker that other times, but I think thats an issue with decals itself. But I can try to modify the Materials to also have Diffuse Information to look less black, have to experiement a bit with it.