Hi Avik,
Thanks for your complete answer and for the grasshopper file you made for me. I’ll give it a try and come back to you. I was actually thinking of exporting the geometry as DWG from ArchiCAD and import it in Rhino. It won’t be a “live Connection” but at least it could be faster to get the geometry. I’ll come back to you if i’ve found an easy way to import with DWG to Rhino.
Regarding the gbXML, in ArchiCAD there is no native gbXML export function so you need to install something else and not sure how the result from gbXML will be. So later I could give it a try, but there are many other wy Before this one 
Yes, it’s seems a long process in case of different wall, so actually it’s faster to assume all internal wall to be the same.
And for the last question it was about the Daylight simulation. When you perform Daylight simulation you need to know the reflectance of the internal surfaces (Wall, floor, ceiling, etc…). So in some cases, you have internal wall in the middle of the zone you have created so I was thinking if it could be possible to add those wall within Grasshopper directly with an automatic process. But I don’t think so it’s to create them into Rhino manually.
So for energy simulation it could be possible but then, we can’t use this process for Daylight simulation.