Also the question isn't whether you are fine with a minority, it's whether you are fine with a small minority, possibly just the Vulcans. If people need to wait until 45 to get a shot and then spend 10 years in the seat they are 55 by the time they can advance to Commodore, 60-65 when they make Rear Admiral, and in their 70es before they can be considered for Vice Admiral. Only a few non-Vulcans would stay that long, Sulu has very much been the exception. Non-EC people can already make Vice Admiral in their early 50es. If they get their shot in the EC at 38, then spend 5 years and make Commodore at 43 they can make Vice Admiral in their 60es, and are at much less of a disadvantage compared to former superintendents and such.
Have you run an analysis of the people who've gotten promoted
out of the Explorer Corps captain's pool? Quite a few people become candidates before 45, sometimes well before. And quite a few re promoted up and out of it before 55.And that goes double for the ones who have useful skills other than, specifically, captaincy (e.g. politics or engineering).
There are a few specific individuals whose rise through the ranks probably HAS been delayed by time spent in the Explorer Corps pool (McAdams comes to mind), but when it comes to the bigger picture, I think you may be barking at shadows.
I don't think there's a lot of evidence that the mere act of
being on the Explorer Corps captain's list without receiving a command is, in and of itself, enough to delay your promotion track. Quite the opposite, given that as far as I can tell, almost everyone who was on the captain's list six or seven years ago, and didn't receive a command, is now a commodore.
If we make 10 years the average rather than the exception that means we both halve the number of former EC captains and lower their average rank, because people end up spending much longer at captain, both waiting for a posting and then in that posting. That means it gets much harder to fill our senior postings with people with EC experience. I'd much rather give everyone skilled enough (that is with a decent bonus) a 5 year turn and then let them get on with their careers. Do you want most of our rear and vice admirals to have had an EC tour, or only a small minority? Voting for ka'Sharren and Straak is vote for the latter.
Put this way. In 2315 we'll have three explorers that've had three five-year missions each, I think two that've had two, and probably about two or three more that will be on their first. Of those, even if we re-up Nash and Straak for their third and second missions, that means we'll have cycled through the Explorer Corps...
Nash, T'Lorel and Straak, Eaton, Ajam, and McAdams, Thuir and his replacement, Saavik and
her replacement, and the first commanders we've appointed to two or three more fresh ships (
Stargazer and, in all likelihood, at least one or two more). Assume three for the sake of argument.
So, twelve or thirteen captains. Ajam may or may not resume service- assume she does. That gives us a dozen or so highly talented senior officers propagating up into the rank structure, the first of which have already started moving. After
that batch of five-year missions (the ones running in 2316) wrap up, we'll have another tranche of about seven or eight more such captains coming up for promotion.
During that time (and counting the conclusion of the five-year-missions of ships that will be wrapping up after 2315), the Explorer Corps will have racked up a total of 3(15)+2(10)+(15, I think) makes roughly 75 to 80 ship-years.
Average tenure in command of an Explorer Corps ship will be a little over six years,
greatly skewed by the anomaly that is Nash ka'Sharren. The median and mode will, obviously, still be five.
By contrast, if we'd replaced Nash with someone else (who?), and replaced them and Straak this year, the average would be five instead of six, and we'd have (say) sixteen potential commodores and admirals instead of thirteen. Plus a
LOT of other senior officers who we just plain never wanted in charge of an Explorer Corps ship, but who are still highly talented and competent- it's just that their skills are in areas like R&D, bureaucracy, shipbuilding, or theoretical tactics and analysis.
So the 'choice' here is between having, say, 16 senior officers with Explorer Corps experience, versus 13.
This is not a very big difference. We can afford to compromise on this issue, in the interests of ALSO establishing that the Explorer Corps is a place for the very, very best of Starfleet, where even unusual individuals who don't fit the "average" template of the fleet can find a refuge as long as they're good at their jobs.