But they can't take 'woman', because we're still using it.
Some would counter, well you can use "cis women".
Except that doesn't work, because it isn't fully inclusive of all female-bodied people. (Including many here, as well as all the non-binaries etc).
A term for "female people who believe they're women and that's what makes them women"(*) is far less useful than a term for "all female people regardless of what they do or don't believe".
In almost every situation where someone attempts to use "cis women", the resulting sentence ends up less accurate than if it was replaced with "women" with the adult human female definition.
(*) and often roping in "female people I insist are covered by this term because I know they're female, even though they insist they don't believe in any of this nonsense and I insist it's impossible to tell anyone's sex"