The idea behind weight reduction is to not rely on just a single factor. We can make lighter components by using better materials such as High Tensile steel. We can use fewer components by removing unnecessary features like seat heaters. We can reduce body weight by using fewer panels or by replacing rivets with glue.
The list could go on forever, but keep this in mind: a lighter car is NOT a less safe car. Lighter cars are more agile and have less braking distance which can make them safer. Not to mention it is usually the use of safety attributes such as crumple zones, ABS
, airbags, etc. that determines safety.