when you create in the original file all Objects related to the elements as Collections, meaning the Wall with the Door has a Collection which includes all original elements without Merging or Apply Modifiers to them, just the original elements.
now, when you arrange each Object as Collection with all it elements and import the Collection as Linked you will have a Collection in the new Blender file and you can Duplicate the imported new Collection, scale it, rotate it, move it and any other transformation without the need to do “Make Proxy”.
each update in the original Blender file will update the Linked file.
you will see only Collections and you will enjoy better way to work without the internal elements spread around and messed up.
Enjoy.