The relevant test in this report simulated a single-vehicle impact. The best insurance policy against kangaroos/deer is a modern, safe vehicle with crumple zones (and, y'know, an actual insurance policy that you'll live to collect).
A problem with hitting a deer, especially in a car, is that the bulk of body mass is sitting just above hood level and will therefore impact directly on and then through the windshield at the driver. Crumple zones won't matter.
