Hey, I've got some funky questions.
I've got a misogynistic maga. (Like so many women I know, she hates women.) And it's occurred to me that she might prefer to be a man, or at least give it a try.
MuCo allows her to completely alter the shape of her body very easily. But MuCo doesn't allow for increases to physical characteristics, so I imagine the shape-changing spell to be superficial and not adequate to changing sex. It could change sexual appearance, but not generate even remotely functional reproductive organs.
To increase a physical characteristic, one must use CrCo. Would a woman need CrCo to become a man? Could PrCo make a man into a woman? I'll give my theory for comment. (All misogyny here is Aristotle's, and none of it is mine.)
Someone might say that one's sex is part of one's essential nature. That seems wrong to me; essence is genetic nature and men and women have the same one. Both men and women grow from sperm, it's just that some of them grow better than others. The cause of sex is the mother's body: sperm are perfectly human, but some live in ill-formed wombs that deform them, and they become women. Sex is an accidental, not an essential, trait.
However, I could definitely see a functional sex change from woman to man violating the Limit of the Divine. Semen carries the human form, which is the soul. Only the Divine can create souls. To make a functional male, then, would be to make something that the Divine uses to make souls, and that's the prerogative of the Divine. So, no making functional men. Likewise, no making functional semen. (Every sperm is sacred!)
But there's functional and there's functional. I can imagine using MuCo to change the appearance of the body from female to make, and CrCo to make the body sexually functional, though sterile.
Making functional women would be much easier: a woman is a place in which a very tiny human being, a sperm, matures. Likewise, one could use PrCo to turn a man into a woman, by destroying the reproductive capacity. (Base of level 20: destroy or sever a limb, would be the starting point for the Emasculation spell.)
While you could just have a long-duration spell to affect the change from man to woman, you would probably need vis to make a woman who could produce breast milk. (Speaking of which, what is the form of breast milk? Corpus? Animal? Aquam?)
Anyway, my somewhat sex-obsessed character eagerly awaits reports on her prospects.