A idea that might be useful
I added this to a application but when the large file comes in from civil or arch a original copy is saved and a bunch of clean up and all the entites in the xref are put on 1 to a few layers so 200 layers are not brought in. Then using a command you can hover over entity in xref and the tool tip displays the layer name from original. Basic idea is a copied drawing and both entites have same handle. And ability to change the layers to what are in original, but deleting then adding objects in modified xref has not yet been a issue.
