We work with Autocad also, but people make "hatching"/fills there, so it doesn't count/calculate the areas in meters square. Can you make converter from hatches into zones?
And by the way, converter from fills into walls will also be good idea. convert fills into floor/ceiling. Converter of "hatching"/fills into roofs. etc.
Main idea is, if Archicad converts from some 3d object into 2d, and additional info is lost, there should be a way to convert that back (semi)-automatically to 3d objects. Well, there should be some conditionas. Especially for walls. To convert automatically from rectangle into a wall, this rectabgle must have certain ratio of width/height (though, some walls may look like pillar). Convert "hatching"/fills into a pillar etc.