I figure there would be Matter and Antimatter feeds going up to the nacelle tanks, a power feed to operate the nacelle, control circuits and maybe a Matter and Antimatter overflow/return feed coming back down to the engineering tanks.
...Plus some way for people to access the nacelle, as in "One of Our Planets"?
Or is TAS outside the scope of this project? On the conceptual level, I mean. The "sets" from the animations may significantly differ from the TOS ones in dimensions, but that could be attributed to the extra artistic license inherent in the medium, even when keeping the actual features such as a holosimulation room, a number of engineering details, and the shirtsleeves access to the nacelles. Or attributing some of those to refitting between the shows... But I'd think nacelle access would be an original feature nevertheless.
Seeing how the red outlines mesh with the, well, mesh, is going to be exciting. Too bad that red is the color the least systematically compatible with the idea of hatches: we have individual curved red lines under the saucer, an outline that gets broken by the pylon on the nacelle underside, and finally a fairly inconvenient reproduction of the stern undercut red square in the E-A wherein the line again gets broken by surface detail.