FYI
I expect that most of your area calculations could be made by applying the appropriate ZONE(S) to specific areas, then using the schedules to sum the areas as needed.
The room wattage problem can be accomplished via the EXPRESSIONS feature. I made a similar feature to calculate the different wattage's required for each room type (zone) between incandescent or LEDs using expressions.
However. expressions are limited, at present, to the properties of a single object and therefore could not be used to calculate area percentages. For that, you could use the new PYTHON feature coming in 24. The scheme for the pending new feature is listed on Graphisoft's PyPi.org site.
Gerry
Windows 11 - Visual Studio 2022; ArchiCAD 27