From what I've seen and experienced first hand only using quality PPF, it'd be a mess. Technically, the PPF is already multiple layered (assuming XPEL, etc). They do sell several variations of films and some are thicker than others.
Additionally, part of finishing PPF is using heat. Assuming you're applying adhesive backed film on top of adhesive backed film, I'd imagine you'd run into all sorts of issues with respect to the glue setting to the paint, edges peeling, etc.
Clearly YMMV, but give it a shot if you want.