I do not think this is possible for technical reasons for now, even if I guess rojig could be useful for that. There is regular Fedora for that. And having a dozen or so of images is just gonna make everything more complex and requires much more tests.
I am definitely advocating to have a minimal version where a desktop environment can be added on top. Ideally, on installation time you could just be asked which DE you want (if at all), and then it creates an rpm-ostree out of that which is your base or something.
Other DEs could just be not supported but it’d be nice if you didn’t have to go for full-on GNOME right away. Personally, I prefer to not have a DE and just build my own out of scripts, a file browser, a window manager, and some two or three other apps.