My rear bumper core support was simular to that. Only rust on the car when I had it repainted. I seperated the core support from the skin, cut away all the cancer to leave the basic shape of the core. It was still intact enought as a skeleton to properly hold the skin and properly fasten the assembly back to the car. I figure it offers as must protection as the front bumper since the bottom was cut away for the IC core.
Must have cut the total wieght by 50% over a completely stock rear bumper.