I'm still waiting for you to explain to me just which part of Rand's character--established
or intended--is in any way incompatible with her being chief of security (note: "It's 1964" is not a character trait).
How about
Yeoman to transporter chief?
Or
Navigator to Security Chief?
You really think I'm baiting you? I don't. I find myself reacting very legitimately to your knee-jerk objection to Janice Rand being anything OTHER than Kirk's personal secretary squire/girl with nothing better to do except make the Captain feel better. The franchise has been rebooted, I think we can do better than Communications Officer after a forty year career.
Don't forget O'Brien's tactical officer to helm to transporter chief to chief of ops/engineer. Personally, I don't find that level of breadth credible and it annoys me. Characters are only defined by what they say and do. I prefer them to be well defined within a fairly narrow margin. Rand's 'transfer' was really just a way to bring the actress back as a guest star in the Phase II series, although I think she was initially in the script as Uhura's relief on communications (a post which she later filled in STIV and STVI). It may that they they felt the role of yeoman was a bit too menial for a 47 year old woman?
Troi's problem was that her role was defined as plot device empathy and fluffy counselor, which only has enough breadth for a guest character. There's a narrow definition and then there is so narrow that you serve nno useful purpose most of the time. Travis suffered from this problem too. If they'd toned down Troi's empathy, formally defined her as the ship's diplomatic officer, treated her as an officer in a proper uniform and not a civilian showing off her boobs, and let her take the lead in more negotiations instead of just standing around and offering a line or two of advice to Picard, then I think the character would have been fine.
I disliked Chekov's career path because it lurched backwards and forwards without any story logic. Now if Chekov had remained the navigator and Ilia had been written as security chief, that would have been fine because Ilia had no back story or established personality to flag up an incongruity.
I agree with you in that there is no reason why Rand can't be trained in security instead of engineering - her engineering career is not an iconic part of her character. However, I see no reason why she has to be security chief. She is best known for being YEOMAN Rand in the same way that Christine is best known for being NURSE Chapel.
Now, I'm not as endeared with leaving Chapel as a nurse simply because it will restrict her usefulness and ability to interact with the wider plot unless they introduce a disconnected scene like Chekov's sudden talent with transporters. However, we already know that Chapel's fate has been sealed by her name-check (I'd have preferred a brief scene where Ensign Chapel from life sciences was drafted in to be a nurse by McCoy personally).
Conversely, as the captain's yeoman, Rand's role is far more flexible. She can interact with the other characters on many different levels in many different locations and she has a convenient reason to be at Kirk's side both on and off the ship. She can be a kick-ass security guard without the baggage that comes with security chief and the ability to develop a more personal realtionship with Kirk. Plus, as with Tasha, it isn't the role of security chief that has any inherent worth (TOS barely used one). It is the personality and the way the character is written into the plot that counts.
Personally, I'd prefer to see a new (female) alien character (from an established canon race) as the chief or as an established guard to add a bit more sexual and racial diversity. I have a real soft spot for Rand though. Her role as Kirk's aide was underdeveloped through no fault of the actress or character (she still had more established personality than Uhura and Sulu combined). I'd like to see the role developed in a modern context as one of the minor supporting crew characters at least.
