Ok… finally found the time to look at this and… it isn’t pretty. Anyone who models chain link or wire grids as an actual geometry deserves a special place in hell…
But I think what I’d try is individually composing each model direct shape as a direct shape in a new family, and save the family to a new location. The code here might be a good start: Revit DirectShape from Curve - #7 by jacob.small
Once you have the families in each document you can save out the library, and then load those into a single model. Names can be derived from each IFC import with the file name as a prefix to ensure that you don’t have any duplicates. And then… viola! you’re federated as a single model.
I still hate the workflow (everything in a single model with this level of detail will be of minimal functional use) but it should work.