I’m curious why it sounds painful to you. I didn’t mean to imply we should reimplement XSLT in JSON syntax, just that some JSON description of a stylesheet, to be applied to JSON data, could be useful.
It very well might be. My feeling was just more or less: I don't love JSON syntax or the tendency towards big, hierarchical JSON documents overmuch (though it's certainly been a massive real-world improvement on XML for most of the overlapping use cases I'm familiar with), so describing transformations on data in it sounds likely to be unpleasant.
Perhaps one of these decades I will actually learn a Lisp.