Families and tradesmen, likely physically disabled people as well. You could make exemptions for people who actually need bigger vehicles, but that just means yet more bloated bureaucracy.
It does not need to be that complicated. Just give families, special needs groups etc tax credits or direct payments and have them decide how to use it. Then families that do not _need_ a large car wont buy one, because they can still save taxes if they do not do it.
Good luck figuring out who needs a truck to transport generators, materials and tools and who doesn't. Just more bloat to chase some low-impact goals of activists who found a new group of people to pick on.
The idea was: give all (relevant class) people a bonus that compensates the tax. If they can forgo the car, they get more money. If not, they break even.
relevant class: big families, construction workers, whatever
I think I'll skip on stealing this idea.