Hello:
In my experience, importing single models from a BIM Library isn't a problem. But if I try to import an entire building, for develop an extension for example, is completely a nightmare. ( adding to this, people that work with REVIT comes from AutoCAD and you know what's mean that).
Well, technically speaking, when import a REVIT file, grows and grows. And all are meshes. VectorWorks prefer work with generic solids. Then it is not a good idea import it.
The last file I try import from a 144.3 Mb rvt file, grows to a 1.2 Gb