@dexterk said:
extracting a footprint, over several levels if necessary, building the component and putting it back in the same spot is what I think you're suggesting.
Yes, exactly. I have been using this method for various (usually complex) sub-structures successfully.
Another "easy" way of doing it (as per Dave's popular method) is to create the component - then make a copy outside of the region of your complicated model - modify this copy (and the one in place will naturally reflect all modifications)