IF you waited until you got in the SD bumper kit, mounted it, then fiberglassed the whole thing in so there were no seams and made it look like an aftermarket bumper I think you would be ok. Fiberglass is strong and flexible, so " I " think it would work and look nice. Plus save on buying a new bumper. You would have to go over the inside on the broken areas to reinforce them as well... Keep it from moving and breaking while highway driving.
This is MY non-professional opinion. Dont blame me if it doesnt work out the way I said. Just 2 cent