I suggest that you use the layout method [sort of like cut-and-paste] since your output is only required to be a plan and not mess with the model at all as was suggested to you.
-- arrange a layer combination that doesn't show interiors to act as a site plan.
create a view and layout for it.
Then place floor plans for each of the buildings on the layout where they belong within the site. Perhaps a floor slab is a good placement cue.
This is all hearsay - others here will have more specific knowledge.
Dwight Atkinson