Soft Body Physics are the last thing you would want in your racing game! EVERYTHING would ruin your car.
That would be a nice feature, but I don't know how much it would actually be used. A few leagues may use it, but I imagine most would not. For realism, it would be fantastic though and I must admit, I would like it. Heck, maybe once everyone got used to it, it would be used more than I think. It is very interesting.
If you do barrels it would be nice to see what kind of crease or when striking the wall, finally there is plenty of options on the Reflective well. But would it not too CPU intensive?