Safety comes from design and the use of exotic materials, carbon fibre, bonded aluminium and such. Light cars that are safe are around already. Take the Smart roadster from a few years ago, great idea. Small safe roadster, light in weight small efficient engine spoilt by horrible gear box.How do you make them safe at low weight? In a crash, that is. Once you get on the highway, low weight doesn't really make much difference. One would wonder why we don't stamp dimples in car body parts yet as that absolutely increases cruise efficiency.
Give the design to Ferrari with a price point north of £150k and what would you get?
The technology in these high end cars is utilised to carry around 5 litre v8’s leather seats ac. If a car was designed from a clean sheet of paper to be a light weight simple car, a Lotus Elise springs to mind, it may be possible.
They do build specials like club sports and stradale but they are based on the “standard”car which needs to carry all the luxury items.
A light car with any power train, be it EV, hydrogen or ICE would still perform better than one that was heavier.
In a lot of cases this technology starts as pie in the sky thinking and is expensive but the more technology is implemented the cheaper it becomes.