I certainly didn't mean to offend anyone, and apologise to those who find women's issues unpalatable.
Neither Andrew nor BC managed to answer my question, though -- which centres around the women-specific hakama rule.
I've just come across a passage in C.M. Shifflett's Aikido Exercises for Teaching and Training
(1999) that says:
Americans might recall that in the US through the 1940's and 1950's, women in pants were considered improper or downright immoral. In some areas this is still true. However, to many Aikidoists the "hakama for modesty" rule seems a tad odd when ladies change after class into shorts and tank tops.
If C.M. Shifflett is female, the book doesn't say so but I believe her first name is Carol, then at least I've read one explanation from someone who is female and it makes more sense than others I've read or heard of.
The point of this line of discussion is for me to confirm that this peculiar women-in-hakama rule was to keep women on the mats for more extensive lengths of time than what might have otherwise have been possible.
In other words - it's not to mark women out for special treatment, or to patronise them with a uniform that's normally reserved for higher ranking students, but to give them equal access to mat-time.
It's the optimist in me trying to interpret the rule positively, in contrast to the interpretations I've heard in western countries associating it with stories of Japanese male chauvinism.
As far as the reasons for dropping the hakama requirements from kyu-grades, I remember reading in Pranin's Pre War Aikido Masters
that this was especially practised in the USA because hakama were difficult to get hold of and therefore an unnecessarily expensive item for beginners.
Thanks for your comment, BC, I'd never heard about the gi and hakama originating from women's clothing. I wonder what the men wore for martial arts training - perhaps armour.