With my family having just experienced a 50 mph broad side crash, you will never hear me complain about the weight of a modern vehicle again. They needed every air bag and ounce of metal to survive. Everyone needs to understand this.
Our other vehicle is a Denali. Many have asked if we'll replace the Sonic with a 'safer' vehicle. Here is the same impact with a taller, heavier Denali.
The penetration into the passenger compartment is higher in the SUV. It didn't move, the rollover doesn't count as it is a result of not moving, so the impact energy is all mostly absorbed in the sheet metal. Crush zones, exotic metals, air bags, belts, seats and advanced engineering modeling have made car substantially safer. That said, if you look at the frontal offset crash tests, bigger is clearly better. Pick your poison.
Back to the Mustang. It appears by the reports it is still running conservative width front tires. That will hold it back.