Question Using LOD(lowpoly object) as fake shadow casters for Highpoly object

Hi all, I have been experimenting with shadow, light and render layers but I can't seem to get what I need.
In our FPS game we have a big city that you can explore and we use one directional light with realtime shadows. Baking light maps is not an option as our game is heavily stylized and the map is huge and till the very end the pieces in the environment will be moving and iterating.

For every building we have a custom LOD mesh that only follows the silhouette of the building and I figured it would be smart to use that simplified mesh to cast shadows as it will generate less tris.
Main goal is:
-Building LOD0 to receive shadows from itself and other objects but to not cast shadows on other objects, and also accept light from the main directional light.
-LOD1 simplified mesh to be shadow only or not rendered but to cast shadows on everything except the LOD0 mesh.

If anyone has any experience with this I would really appreciate any advice or work around.

Cheers