I may be biased coming from an environment where everything was extremely well documented, but nothing can replace an accurate drawing. For something like receptacles, the only way to show it with no ambiguity is an actual labeled map of the building, with each receptacle, where it's fed from, and how the wiring is configured. I'd go as far as to say it should be required by building code to be updated to reflect as-built condition. Not necessarily full engineering drawings, but at least accurate and legible shop sketches.
And yes, I know this would be very difficult to do "the way it's always been done", but I contest the way it's always been done is wrong.
