Ok folks, we now have rubble for destroyed structures as of r12718 The idea is rubble is spawned when a building is destroyed, it looks like burned/muddy ground and bits of wood/stone debris. It lasts for a predefined time (currently 10 seconds) before sinking slowly into the ground and disappearing.
But we're currently reusing foundation actors for this since we have no rubble models yet So let's work on that! You know you want to right?