I have extended the historic building to encompass the new gallery (building outline) and added all individual buildings as parts. A single entity for the entire gallery, historic and new, seems more important than separating by internal detail (south & north building).

The north building (complex) could be combined into a single part to have only two parts (south, north) and be named individually but I'd argue including the "north building" and "south building" detail might unnecessarily clutter the map.

I have not touched the construction site between the two complexes (and gates locking the various paths around it) for now. Is the Bing map showing the final construction? Happy to add.