For example, the universe should not have to explain why so many people look like Diana Muldaur.
Of course it is explainable in-universe why two people
in TOS look like Diana Muldaur - they just do. Do you think it is that uncommon for look-alikes to exist?
At that level, where there are no physical differences whatsoever? Yes, I do. Even identical twins are generally distinguishable on some level, and they are genetically identical (and usually share common nurture as well as common nature).
Furthermore, the odds drop to the infinitesimal once you start saying "two identical people on one ship, within just a couple of years' time" and then another identical person on a ship with the same name, a number of decades later.
To claim that such a thing is plausible is just... wrong. No, we have to accept that what we're looking at would never happen in a "real-universe" version of Star Trek. The people might be "somewhat similar" but not identical.
You can also argue that it's odd that Zephram Cochran changes appearance utterly, and ends up looking like a number of alien characters who showed up on the 1701-D at various times. Or how Spock's dad was such a dead ringer for a Romulan naval commander, or so on and so forth.
We either abandon all pretense of "willful suspension of disbelief" and never watch it again without viewing it ONLY as an exercise in TV-show production (without regard to the story being told), or we excuse the "wrong" bits in some fashion in our minds' eyes and "rewrite" the objectionable bits... but only rewrite as much as is necessary in order to have it make sense to us.
Some of us... those who, like me, tend to get very deep into the technical side of things... tend to overwrite the technical bits a bit more extensively than others do. And I think MOST Of us in this forum are like me in that regard.
I wholeheartedly agree.. "the universe" (the TREK in-story universe) does not require Diana Muldaur to play each part, or Mark Lenard to play each part. The "real" people would likely bear less overall resemblence than the "recreated, acted" versions do.
See, that's how I watch the show. ALL of the shows. I view them as "historical recreations" for entertainment purposes. "Holodeck programs" so to speak.. based upon what information is available, but occasionally abandoning "real universe" bits in the name of "storytelling." And some storytellers... like whoever was tasked with telling the story of the alien race who used Spock's brain to drive their planet-wide computer network... got retold in, shall we say, less successful ways than other stories got retold.
Something more challenging would be in TOS what the odds of two or more planets developing exactly like Earth, with one even having the same Declaration of Independence If anything, the odds are "out of whack" in TOS
Well, this is either "bad storytelling" (something similar, but not identical, "really" happened?) or it's "incomplete storytelling" (meaning that there should be some science-fiction explanation for how somehow, a space-time event occurred which caused multiple near-identical copies of Earth to be created, which our crew occasionally come across?).
But in the end, I prefer the first option. I can accept that whole episode, if the EXACT WORDING of the US historical documents is removed, and if the people are no longer southern-Californians, and if the "parable" nature of the story is a bit less bluntly in-our-face.
These stories aren't always bad. "A Private Little War," for example ,was a much better parable, and that's in large part because it was less blatantly preachy.
Its only when we say that there is no "personal interpretation" possible, or when there is "official reinterpretation" which CONTRADICTS elements seen on-screen, that we have problems.
SO... back on topic...
We don't know what the panels really are "in universe," and if you want them to be sensor system windows, more power to you... unless you get onto a production team and try to "formally redefine" this to say that EVERYONE must accept your personal interpretation. Then, and only then, will people have the right to argue with your position.
And that brings me back to my very earliest point - all we REALLY know is that they are made in the exact same manner, and have the exact same appearance, as the "windows" on the 11-foot model, and thus I am convinced that they are intended to represent windows on the real ship. And because they face upwards, and because human psychology would be best served by having a few open spaces with "sky" overhead, I am convinced that they are for that purpose. But nobody else has to agree with me. Even if I know I"m right and you're all wrong!