It would appear I've misquoted the very source that I used. Upon re-reading it more closely, it doesn't actually say that Spock's role was originally meant to be female, but that she was asked to read lines for the that character's role and that the XO was originally meant to be female (which is something we already knew anyways). That's why I get for getting ahead of myself. I retract that statement.
I'm quoting now from the Star Trek Encyclopedia, the Updated and Expanded version, which states, in the entry for "Number One" on page 328-9 that the "character was dropped from the original Star Trek series at the insistence of the network, and Mr. Spoke was "promoted" to second-in-command." It goes on to state that there would be no female in such a position of authority in Trek until "1986, when Madge Sinclair was cast as the captain of the ill-fated U.S.S. Saratoga in Star Trek IV." I know you've already acknowledged that, but bear with me for a moment. The source that I've linked to, which in turn cites Leonard Nimoy among others, ties the decision to switch the female uniforms from pants to skirts into the decision to banish Majel Barrett from the position of Number One, and strongly implies, though it does not directly state, that the second decision occurred for the same reason as the first.
Clearly, there are multiple competing theories behind the treatment of women. I have obviously decided to buy the a particular line, while you have been persuaded by evidence pointing to another conclusion. I'm not sure if we can reconcile the two, though I'm willing to listen to further evidence to support your line of thinking. If you used to believe as I do now, I'd like to see what changed your mind, though I can't guarantee it will do the same for me.
Still, thanks for the reading material. I don't have immediate access to Inside Star Trek
as it's not available in my local public library, but I'll think about buying it on eBay or something. I do consider a discussion on the gendered discourse within Star Trek to be vastly more interesting than drooling over pictures of semi-naked actresses.
If you deem this suitable of further discussion, I would be happy to engage in a separate thread, so as not to drag this one any further off course.