Last night and this morning, I gave some thought to the Janice Lester question.
Memory Alpha article aside, I don't recall any canonical reference to Lester actually serving in Starfleet. Can anybody else cite anything?
In the absence of any evidence, I propose this backstory:
Kirk, Lester, and Coleman all met as Academy cadets. They may or may not have had some shipboard service together, but Kirk and Lester had a brief romance, with Kirk concluding that Lester was mentally unbalanced, and most likely sociopathic. When the time came for the "psych test," Lester failed miserably, and was excluded from entering the Command track. She convinced herself that she was being singled out because of her gender, challenged the ruling -- the first sexual discrimination suit brought against Starfleet since pre-Federation days -- and lost, badly. She briefly investigated gender reassignment surgery, but even in the 23rd century, it involved a lengthy preparatory/screening process, and the permanent loss of the ability to produce offspring, and between that and the general consensus among her doctors that it would do more harm than good to her chances of getting into the Command track at the Academy, she gave up, left the Academy, and pursued a Ph.D. in xenoarchaeology at U.C. Berkeley. But she never gave up her delusion that it was her gender, rather than her sociopathic and emotionally disturbed nature, that had kept her out of the Command track at the Academy.
Coleman was smitten with an unconditional and utterly jealousy-free (but entirely unrequited) love for Lester, and after bouncing around among minor Starfleet postings, culminating in his being dismissed from a CMO posting for incompetence, leaves Starfleet, finds that his reputation has done him little good in civilian medicine, and signs on to Lester's expedition to the planet that was the subject of her doctoral dissertation, Camus II.
Several years into the expedition, Lester makes a discovery: while the ancient civilization there had never managed to discover a FTL stardrive, they did manage to discover a way to exchange minds between bodies. No doubt the discoverer of the underlying principle feverishly developed a practical version as a way to save the life of a beloved, but terminally ill, spouse, and at first, the technology was only used to save the terminally ill by transposing their consciousness into the bodies of condemned criminals, but almost certainly at some point, the Camus II rulers used the technology as a means of achieving immortality, leading to tyranny that almost certainly doomed their civilization.
Lester, after using members of her expedition as unwilling guinea pigs in her experiments with the device, deliberately exposes them to celebium radiation, first to test whether the death of one member of a transposed pair would make the transposition permanent, and then to silence them. By the time Kirk arrives, she and Coleman are the only ones not either dead or dying of radiation poisoning. And the rest is canon.
"You cannot write in science fiction (...) without realizing that sexual equality is as basic as any other kind of equality. This does not mean that in future pictures I will ever stop using women as sex objects, as I will not, but to be fair we have always used and will be continuing to use males as sex objects, too. As a matter of fact, when I was younger and much more agile I've been used as a sex object myself; I think it's great fun.
- Gene Roddenberry