Actual canon and creator intent said Pike's first officer's name was literally "Number One," what's your point? Dialog, too. "He did his residency on Vulcan" plays very differently if he's a thirty-year veteran physician who should have plenty of accomplishment McCoy can use to reassure Kirk than if he's a newly-minted hotshot. If they're the same person, it goes from "the kid knows his stuff" to "he may have peaked thirty years ago, but he peaked in the right place to make sure Spock's in good hands."
Actual Canon: "Such Sweet Sorrow, Part II," Number One gives her name as "Number One." Creator Intent: D.C. Fontana and Majel Barrett both explained variations on the concept that her planet was a pure meritocracy and she was literally named "Number One" because she was all-around the best of them.
If Boyce showed up, theoretically, he'd be different from he was presented in "The Cage". So you can't really go by how he was presented in 1964. If we went by that line of thinking, we'd be judging Pike by his stupid "I can't get used to having a woman on the bridge" line. They changed Pike for the better. If SNW ever had Boyce, they'd change him for the better too. As far as M'Benga: do we know it's even the same M'Benga? Maybe medicine runs in the family and he has a relative serving aboard the Enterprise during TOS. Probably not, but it's a possibility too.
Just a thought on all of the Star Trek "demotions." If the Federation no longer uses money and nobody gets a paycheck, promotions and demotions would presumably mean a lot less to many people. Sure, there's the "status" of being in a command or other high-level position, but I could easily see people try things for a while and take a "lower" position that they enjoy more. Hence, there is no reason that Boyce and Dr. Crusher might not take a position for a while and choose not to stick with it given that there is no financial penalty associated with doing so.
No canon evidence, just common sense. It's a top Starfleet billing, responsible for the health and safety of literally millions of personnel. It wouldn't make a lot of sense to have that position be filled by any other than a flag officer. Oh? How so? Boyce doesn't need to be cancelled. He didn't act anachronistic, offensive or any kind of stereotypical 60's attitude. As we saw him, he's a good officer (good enough to be included in the ship's command briefings, which doctors rarely are), Pike's best friend, and an excellent doctor. If he were to turn up on SNW, he wouldn't need to be any different. Perhaps Beverly was called upon to temporarily fill the post while a new, permanent officer was found.
Because he will be played by a different actor who will bring his own mannerisms, style of speech, and aged a little more, reflecting the deeply profound truth that people change, even in small ways. This isn't about cancelling or whatever. Just that, by the very nature of recasting, he will be different.
^ Oh. Yeah. Right. I do get that. And again, I totally called it: Len Cariou. (Provided Blue Bloods would be amenable to loaning him out, of course!)
One wrote for the character and the other was the first performer to embody the character. I'd say both have some legitimate say - even after death - on how others might write for or portray her.
Sounds more like interpretation of the character written, not creator intent. What did the creator intend with her name?
My point with the Number One example was that just because one thing has been said in interviews and behind-the-scenes documents doesn't make it so conclusively and unquestionably authoritative that it can instantly shut down a perfectly reasonable reading of the actual episodes that TOS and SNW M'Benga are two different people and not the same person who somehow became younger, less senior in his career, and grew up in a different part of the world after a decade.
I only see one person credited as a writer for The Cage, which barring the recycled bits in the Menagerie, is Number One's only appearance in TOS.
Whose to say that Una isn't a word in her native language that literally means One. And the rest is all just coincidence.
Roddenberry was once quoted as saying, "In Starfleet, rank is more like a job description." But the writer of the episode was not necessarily the writer of the description in the Writers' Bible. Majel Barrett took it upon herself to develop Number One's (unpublished) background to approach playing the character, and then DC Fontana used many of these ideas in her novel, "Vulcan's Glory".