If only there were some kind of document or form, let’s call it, I don’t know, a “waiver of liability”, that people could sign, so that such things could be built. Somebody should really invent one. I bet with a form like that, people could do all sorts of dangerous things like jumping out of airplanes or sliding down snow-covered mountains.
Old malls should have some after-life. The (since razed) Eastland Mall ended up as a large indoor flea market, including vendors who took over storefronts (and a functioning food court). Maybe some of that incubator thing as well as art spaces. Stuff like that, plus a bike track seems a very reasonable way to reuse the space. Also, a Museum of the Living Dead.