Apologies for the double post -- I just saw this on another board and it brought my thoughts on the TNG vs Movie Era Warp Core / Intermix Chamber to crystal clarity
Now, let's consider the warp-core. We first saw the glowing tower-whatsit in TMP. In TMP, there's no indications whatsoever that the tower was itself the main-reactor. Watch the movie again. It's pretty obvious that the tower is just a conduit. There's a horizontal conduit in TMP too, & the horizontal one doesn't look any different than the vertical one, so the vertical tower doesn't look any more "important" than the horizontal glowing tube. They're just conduits - in TMP, we never actually see the main reactor itself. It's in the secondary hull somewhere, but we never see it.
Fast-forward to TNG. The set designers & art directors for TNG apparently liked the glowing tower-whatsit from the movies (it does look cool), so they put one in engineering on the E-D. Here's where the writing gets sloppy. The TNG-people decided that the glowing tower thing was itself the main reactor, and thus the "warp-core" was born.
Through TOS and the early movies, the Warp Nacelle were where the reactions were happening. The glowing tube in engineering was simply a conduit. When the set was redesigned and repurposed for TNG, that element became the "warp core." This isn't necessarily invalid approach, but my personal feeling is that it was a rationalization to crowbar in a visually cool element for the sake of having something looking cool. From a dramatic point of view, it makes Engineering more interesting if the super powerful and potentially dangerous reactions are happening in that very area. Even if the prior (and IMHO more logical) intent was that those reactions happened out in the nacelles, away from the crew members, and easily ejected should things go amiss. All the more reason I prefer the TMP style conduit.
I did notice you put a kind of inverted L shaped kink in the Ent refit intermix chamber. I am curious what the reason was (and forgive me if I missed the explaination, I tried going back a few pages). Was it to accommodate that corridor section seen in TMP? Or to match up the the two diagonal conduits branching out from the back of the forced perspective set? Or something else entirely?