I really like the idea of scrapping the concept of "wall" and "structure" and "window". I would love to see it changed to something like "Axis extrusion", "Profile extrusion", and "Opening element". That way they are named after their "geometric" function, not named after their "semantic" function. This would essentially split the toolbar into two halves: "Modeling" (axis, profiles, openings, import meshes, nurbs? part design?) and "Building information" (building parts, sites, wall, slab, window, other). The modeling tools create geometry but building information is not assigned. The building information simply assign building data to geometry. (Side note: I wonder if in IFC you can represent 2D things with 3D lines instead of solids and breps)
This is really beneficial because:
1. It breaks away the mindset that certain modeling techniques only create certain objects. This prevents people deciding to misuse objects for other IFC products. It also opens up people to the idea that there is nothing magical in BIM - it's simply data assigned to geometry, which is true

2. It prevents the problem in the UI where you create a wall and you see it named Wall with a wall icon. However then you change its IfcRole to something else, but it is still called Wall and still has a wall icon. This is really confusing.
3. It ensures that there is a discipline when BIM data is assigned. In programs like Revit or ArchiCAD because the modeling and BIM data is in the same tool, it means that even if you are just rapidly drawing a wall, a bunch of default (and likely incorrect!) data is assigned. This leads to poor quality BIM data. By making the building information assignment explicit, you help ensure that the user takes care to create a high quality BIM model.