[ghusbands]

The usual macros in Lisp get all of the code as data, making rearrangement of the tree fairly trivial. For syntax changes, you'd use reader macros, which essentially involve writing a parser for all the parts that aren't Lisp. Once that's done, which is non-trivial, you would again have a tree to rearrange as you saw fit.

However, you'd be very unlikely to make something as syntactically heavy as JSX in Lisp. Lisp ethos is to keep the syntax as simple as possible, so it stays out of the way.