Yeah, regarding the height of the vehicles, I think they suffer a bit because the infantry are on 1mm thick bases, making them inherently a bit taller than normal. Combine that with the fact that the punks and such are on the beefy side of 6mm and it exacerbates it even more.
The vehicle sculptor actually did make all of the vehicles to spec according to the art. I think it is a matter of us being used to beefier models in epic and what not. Like, a Ford Mustang in 6mm would be about 16mm long , the hot rod above from headlight to turbo engine is about 18mm long, so they are actually spot on with the sizes of non-military vehicles in the real world. Same goes for the teeny post-apoc smart car. An actual 2-person smart car in 6mm would be 8.3mm long, the tiny smart car from hell above is about 10mm long. As a last example, the ninja bikes. They look tiny as hell at 7mm long...but a real Kawasaki Ninja is 2015mm long, which in 6mm would be 6.71mm.
All of the above being said, I do agree, beefier vehicles are more pleasing to the eye. In the future, all vehicle dimensions will be increased to make them suitably pleasing to the eye, just not so big as to be ridiculous, because most of them are still going to be based off of cars.
Dedicated large war rigs will be in wave 2, as will a mega-battle bus, if the artist is of like mind. We'll call this one a light war rig

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