You need those laws, because current situation doesn't fit you. I've heard the tank argument for last 20 years over and over. There are tons of use cases when bigger is required, say bigger family, lots of goods being transported etc. I don't have a big car myself, but such statements are pretty ignorant of reality. and what about all the cargo vehicles, trucks etc?
If you want to punish those evil rich capitalists in good ol' communist class envy way, then I have few ideas - we should ban people changing phones in less than 7 years, have only 1 computer per family, every 10 years, only 2 pairs of trousers, no meat for anybody ever, in fact no car and of course only 1 kid max. Its for the greater good, right?
What Switzerland does is, with its car tax is, at least in some cantons, the tax is calculated in equation which considers HP of the car and its weight.
Or will we slowly move to tanks.