I am driving a 2007 VW Golf. You could make it easily 15 cm smaller by cutting off the center console between the front seats without sacrificing any safety. Of course, the rear bench would be comfortable for 2 only, but that already applies to it as it is. So one could design nice 4 seated cars - especially if they are designed electric only, removing most of the need for the center console, as there is no gear shifting.
