Context: until fairly recently, I worked an implementation of XForms (as the project creator, and leading most of the architecture/design). Prior to that, I inherited maintenance of another implementation, which utilized XSLT[1] as a core aspect of its design.
I’m curious if you could describe more about what you envision. I have a difficult time imagining:
1. How the stateful/interactive aspects of XForms (such as insert/delete, as you mention) would be implemented client side without JS.
2. How XSLT factors into that vision.
It might be lack of imagination on my part! Admittedly, I don’t know everything about XSLT and maybe it has more interactive capabilities than I’m aware of. But at least as far as I know, when a browser vendor did implement XForms functionality it still ultimately depended on JS to achieve certain behaviors. It’s been a while since I was looking into this, but IIRC it looked conceptually similar to XUL. And granted, that might mean the JS is provided by a browser, and encapsulated from user space similar to browsers’ use of shadow DOM for standard form controls now.
1: I also have good reason to believe my work on this prior project helped keep XSLT alive in Chrome the last time there was a major push to deprecate it! Albeit totally inadvertently: my work just happened to correlate very closely to a spike in usage metrics around the same time, which was then cited as a reason to hold off on deprecation.