To borrow a phrase, Fascinating! Loving this thread.
I did find a quote on Doug Drexler's site talking about his cutaway.
"There would have to be an Engineering section in the primary hull (some people refer to it as the “Impulse Deck”). Before I began placing Main Engineering in diagram where I did, I got Matt Jefferies approval. Basically I asked him where Engineering was, and he looked at me funny and said, “In the Engineering section.”'
Speaking of designers intent.