@Clementineorsatsuma and @TeaKlaxon , we clearly have conflicting opinions, which mean this can all get a bit circuitous and emotive (you say tomayto, I say tomahto), so how about trying to resolve this by getting as close as we possibly can to more objective basics?
Clementineorsatsuma - let's take a definitions-based approach, from the starting point of a source I assume you would trust (apologies & put me right if not).
"Cisgender or Cis: Someone whose gender identity is the same as the sex they were assigned at birth" and "Gender: Often expressed in terms of masculinity and femininity, gender is largely culturally determined and is assumed from the sex assigned at birth." (Stonewall).
This unambiguously establishes that in asking me to call myself "cis" to distinguish me from "trans", you are assuming that I identify with "largely culturally determined... femininity". I don't. Not remotely!!!
As such, what about my rejection of this label could be deemed unreasonable or unjustifiable?
TeaKlaxon - in the face of the two-tomah/ay-to stand-off, I think logic may work best here...
You refer to the vital importance of linguistic classes to distinguish between different groups. I agree. "Trans women" is a necessary descriptor for those who identify as trans, and, as I understand it, also accepted by this group (although many members may find "women" preferable). "Cis women" is a useful descriptor for those who identify as cis and, by definition, embraced by this group.
Would you agree that that leaves two groups without a word: women-who-don't-identify-as-cis (that's quite a mouthful, after all!) and the entirety of adult/juvenile human females as a biological sex class?
Would you agree that the former (women-who-don't-identify-as-cis) are as entitled to choose or reject labels as anyone else?
Would you agree that the latter (the entirety of adult/juvenile human females as a biological sex class) need a word to describe them as a political entity? (By your standards, there's currently no single word to, for example, refer to adult human females suffering under Taliban law - both "trans" and "cis" would presume a particular gender identity, and your interpretation of "women" could include males).
As you'll see from the above, I see inconsistencies in, and issues with, your preferred language that remain unaddressed. So, here's my solution.
My preferred language would be:
transwomen = trans identifying male (already in accepted, common use)
cis women = cis-identifying female (for women who choose this)
women = all adult human females, including cis women*
*Note the spaces in the above, which enable the class distinctions your approach prevents - it would require another concession on the part of transwomen, who, as I understand it, often prefer to retain the gap. But then women are making a concession too, in accepting males' use of "women" in the other half of the word. Note, too, that, to the best of my knowledge, none of the terms above are deemed offensive by the corresponding group.
So that's me.
What would your suggested alternatives be, with a view to making these same necessary distinctions in a respectful way for all concerned?