Any week in which one encounters both a female shogun Yoshimune and the frighteningly brainy Major General Olivier Armstrong is a very good week. (Why FMA would not be a happy romp in Japanese: army titles. 'Nuff said.) That anent this metafandom post on authorial intent and female characters. The answer to the problem posed in that post seems to be having series created by women, if FMA and Oo-oku are anything to judge by.
I can't conceive a thing unless I see someone else doing it. Yoshinaga's authoritative, sexual, and charismatic Yoshimune is an eye-opener: how to be a sexual and procreative being with dignity, indeed. The real Yoshimune was rather abstemious in that respect, which I like to attribute to him having a thing going with Oo-oka Tadasuke though I'm sure he didn't. Cold fish, that man. OTOH you can make an excellent argument for Oo-oka having a thing for Yoshimune. Neither, however, was likely to grab unsuspecting gardeners for a romp in the bushes as manga Yoshimune does. On the other other hand it's distinctly possible that historical Yoshimune had trysts in the bath with his (female) bath attendants, since that bit Yoshinaga put in, about several people lying just outside the shogun's bed screens listening in on the pillow-talk in case his partners were to ask him for some special political favour, was a) quite accurate and b) a serious disinducement to copulation. Nobody listened in at the bath, which is why several shoguns' heirs had embarrasingly low-born mothers.