Something just occurred to me: what if Mary Shelley's Frankenstein was, as a whole work, an ironic statement about masculinity and femininity? The female characters are limited to Elizabeth, a blushing flower of a fiancé, and Justine, for the most part. There is mention of his mother, but she dies during childbirth, the ultimate female "sacrifice". But there is a lot of discussion about the female companion to the monster, almost brought to fruition ultimately destroyed. She might actually be considered an important female character in Frankenstein.
My point is the way in which these female characters are juxtaposed with chauvinistic male characters and themes. Victor is full of dreadful masculine personality traits. He is selfish and arrogant. His head is filled with rationalizations and he fails to realize over and over again the consequences of his actions. He allows Justine to be wrongfully convicted and executed for murder, and then stands by blindly as the monster kills his wife Elizabeth. Elizabeth, in fact, spends her time in the novel praising Victor for his decisions or forgiving them.
The monster himself represents some base masculine traits, in his brute strength and ugliness. But he is also representative of the goodness of humanity in ways Victor is not. He is reflective and pensive, often considered feminine qualities in a man. Even though he does bad things, he admits them; Victor merely dismisses or runs from them. When Victor is set to create the female monster, he is fearful she will have the same qualities of the monster, or even "ten thousand times more" (pg. 144). Just to stab home the point of masculine greatness, he fears she may turn "to the superior beauty of man" rather than keep company with the monster, his feminized monster.
I digress. The question is whether Patchwork Girl fills in gaps missing from Frankenstein in terms of feminist theme. Whatever subtlety of feminism Shelley might have achieved with Frankenstein, Jackson does in Patchwork Girl with an exclamation point. Her female characters are strange but instantly likable and respectable. Elsie gives herself to Jackson's "monster", both in figurative and literal senses. Chancy is a woman passing as a man in a man's world - the Sea - and is fascinated by the monster in all her "differentness". Even the women who contributed their parts to the whole of the monster are interesting and reverential.
In general, the female characters are fleshed out, male characters are either ciphers - the "Captain" is just that, "neither maritime or military" without much else by way of description - or feminized - her liver was "donated" by a gay man named Roderick. Interestingly enough, Jackson uses imagery and concepts of queer culture throughout Patchwork Girl:
I am tall, and broad-shouldered enough that many take me for a man; others think me a transsexual (another feat of cut and stitch) and examine my jaw and hands for outsized bones, my throat for the tell-tale Adam's Apple. My black hair falls down my back but does not make me girlish. Women and men alike mistake my gender and both are drawn to me. ("I am", "M/S", "Story")
Female authors often use the language of alternative lifestyle as feminist badges in their work. The masculine norm is to show no attraction whatever to the same sex. On the other side of the pendulum swing is the feminine, whose embrace of self often includes, at least in thought and sentiment, mutual respect and love, be it physical or emotional, for other women.
To answer the questions posed, as they are more direct than some of the other "positions" we've had to take, I say this:
Jackson appropriates for herself the basic concept of Frankenstein - the blending of parts into a whole - to explore gender, among myriad other subject matter, through feminist lenses. Shelley relied on male characters and characteristics to tell her own feminist view; the female characters of Frankenstein behave disappointingly, but perhaps to a satisfying end. Jackson in turn successfully paints female characters and scenarios in Patchwork Girl to speak for themselves an overt feminist hyperfiction. Her concepts are at once naked and in-your-face yet mysterious and elusive.