The Enterprise D cutaway could be seen in main engineering (during 'Generations' for example, when the Duras sisters view it via Geordi's visor). I think (although I could be wrong) that the E cutaway was displayed at the rear of the bridge.
That corridor is not only featured in TMP. During Khan's first phaser strike we see the cadets fleeing engineering and some of them exit through that door and out through the corridor. And I don't think there's even ten feet to spare there. And even if it is only seen twice - well, its still there, isn't it, no matter how many times you see it? And my argument isn't really about storytelling - its about the reconciliation with what is seen on-screen (ie, canonical Trek) with the technical realisation and design of the ship from a practical standpoint. I have seen Mr Probert's drawing and I appreciate that was the design intent. My point is that the intent doesn't mesh with canon, and concepts are simply that - concepts. Not final realisations.
I hadn't considered that drop-down door in engineering, and yes I think you're right - engineering must be lower down. And I'm sure I can't be the first to mention this, but how does that door manage to slice straight though the horizontal intermix chamber?
I wish I had the ability to do my own version! Unfortunately I do not possess the skills that CTM does or the necessary hardware. I think his version is terrific, but I just find that to shrink the torp bay by that much and to ignore an on-screen feature such as that corridor deviates a bit much from canon. Can't wait to see the finished ship though.