If it's not structural, you should be able to wire brush it down and coat with undercoating. If you poke at it with a screwdriver, does it chunk or flake off or just a little dust? That should tell you if it's structural. If it is, it's a hassle to fix. Doesn't look that way from the balance of the car, though. These are pretty tough vehicles to do some heavy winter duty or off-roading.Do you think it would be possible to remove that rust easily and secure it properly with anti-corrosive paint?