Recently, in response to user needs for the SBL style, citeproc-js added support for providing -short versions of all CSL variables, to be rendered with form="short". (https://forums.zotero.org/discussion/comment/324592/#Comment_324592)
In my work on apa.csl, I’m finding that it wants a lot more detailed information for reviews (e.g., medium of item being reviewed, date of item being reviewed), as well as for original publication information (e.g., original medium, original container title, original pages, original editor) than is currently possible with existing CSL variables. As far as I am aware, MLA and Chicago have similar requirements.
I suggest that -short, original-, reviewed- should be expanded so that they can be applied to any CSL variable. This would allow maximum flexibility without having to individually specify each possible variable of this kind.