All your points are worth considering. Ultimately, I don't think the evidence that the Enterprise is some class of vessel other than a Constitution class is actually very compelling. The evidence of that seems to be somewhat circumstantial and inconclusive.
But considering Matt Jefferies' preproduction sketch (if you seriously want to chalk it up and declare it as "fraud", you'd better come up with some solid evidence, please) and the "Enterprise Class" statements in The Making of Star Trek
circumstantial or inconclusive than "Constitution Class", especially considering how this one made it into the world and is now defended at all cost and the expense of the original series' creators and producers:
- The creator of the Enterprise didn't know what he was doing (sketch indicating Enterprise to be the 17th design and the first in the series or "the first bird")
- Producer Bob Justman didn't know what he was doing ("Enterprise Class")
- Stephen E. Whitfield didn't know what he was doing ("Enterprise Class Starship")
While you and others create a lot of imaginative interpretations why the Enterprise
should be a starship of the Constitution Class ("NCC-1700") you fail to comment how these starship registries on the starship status display in "Court-Martial" beginning with a prefix of "16" could seriously belong to a class that supposedly began with "17".
Greg Jein didn't reflect on this issue when he first wrote his treatise, but later - when approached with the issue of the "complete" bars on the starship status display - he conceded that a low "complete" bar could indicate a starship just being built and the lowest bar on this display was that of "1700"! (being the farthest from "complete").
According to Jefferies' nomenclature that would have been a new starship whose last two digits hadn't been determined, yet.
A logical conclusion, especially considering TOS-R, would have been that the Constitution's
prefix began with a "16", too.
The "Space Seed" script mentioned "Constitution Class Starship" and everybody involved with the production would have wondered "What the heck is a Constitution Class Starship" especially since the bridge dedication plaque said "Starship Class".
The simple answer comes from the script itself and Khan stating that he has read several manuals of several starships, of which one obviously belonged to a Constitution Class. Thus, the Constitution Class was merely adding some "flavor" to the fictional universe of Star Trek. If you invoke Occam's Razor, please apply it accordingly.