I can't find the original announcement topic for Arch References... Would I have forgotten to write one?
In git commit 7eccda34d09 the Arch Reference tool now has a new lightweight mode.
How it works:
The Arch Reference allows you to insert, in the current document, an object that is a copy of an object from another file (Part-based or BuildingPart only). If the other file gets changed, the reference will change too (it gets marked to recompute, actually)
Internally it's quite simple, the shape and the color of the target object are loaded from the file (by reading the zipped contents, no actual file opening is performed, which is quite fast) and applied to the reference object.
There were two modes previously: Transient and non-transient. In non-transient mode, the reference's shape is saved with the file ("normal" behaviour), while in transient mode, the shapes of references get discarded when they are hidden (and reloaded when they are made visible again). The file gets much smaller, but there is an additional time to reload when making the object visible.
Now there is a third mode: Lightweight. It doesn't load the full shape of the object, but only its OpenInventor representation. So the object appears in the 3D view, as it was a "real object", but it has no real shape behind.
Note that this only works with BuildingPart objects saved after the commit above, with their "Save Inventor" property turned on.
What happens under the hood when you turn the "Save Inventor" property on is that an OpenInventor node of the BuildingPart is generated and saved in a text file inside the FCStd file. So the Arch Reference object is able to load that file.
To tell the truth, I thought the performance gain would be very high over the "Normal" mode, but it's not that baffling.. I'm curious to see others testing this, though.