I have a big problem with my punto because when my child sits in the back seat it seems she is enormously vulnerable to a crash from the rear. I think she would be better protected if the car had an extended boot.
She also sits on a plastic petrol tank with plastic hoses under the seat.
Unfortunately safety is a luxury feature and life is dangerous.
You say it like its a bad thing, I'd rather have a plastic tank than a metal one in an accident; the tank is more likely to deform and stretch than split and spill its contents.
The video CZenda put up illustrates a point, 5 star Ncap does have its benefits, like being able to walk away from an offset impact with a Volvo but what it doesn't show is the impact on internal organs. Crumple zones are intended to absorb energy, like falling off a building into a crash bag. A rigid bar is equivalent to replacing the air filled crash bag with a yoga mat.
As soon as you introduce rigid definitions such as 'ability to absorb an offset impact at 30mph' you can then tune the parameters to achieve that result. The fact that the same impact at 50mph will liquefy the occupants is irrelevant because there isn't a category for that, it just gets chalked upto a "high speed impact, they didn't stand a chance".
For the sake of the OP, the Punto isn't an unsafe car, but if you equate airbags with safety and that's important to you then you'd be better off buying something with more airbags. Though as the shaved monkey Mr Clarkson once said, cars should have a 12" spike coming out of the wheel aimed directly at the drivers face, only then will cars become "safe".
Whatever you do DO NOT buy a Renault Modus after being inspired by the video clip with the Volvo, they are an absolute pig to work on. You cannot change the headlight bulb without removing the bumper, which is really a main dealer job.