3.7.1 The essence of the ISTC class is competition between realistic models of saloon/sedan cars raced in Touring Car Series for Class Two FIA Touring Cars. Not withstanding this definition , all cars must use a four door bodyshell.

The actual rule is above, and yes it could proberly do with a brush up.
But the last line of the rule is what mainly counts. The reference to "world touring cars series" is to keep the body manufactures in having some realism to there looks as they should be based off a real car, which as we know has become a little vague at times as manufactures have leaned towards the performance side (even Tamiya these days).

A body list can be a good idea, but which one do we use? who will maintain it to cover recently released bodies on the world market? will the scrutineers be able to identify the bodies in use when it is a struggle to get clubs to have scrutineering of an acceptable level?