It was a pretty standard HT cap dielectric for years.
Depends on the current, voltage, area, acceptable error factor and amount of damage acceptable in catastrophic failure : ) Will it work? Yes, to some extent. Reliable or repeatable? Well, everything depends on your skill at that point.
+1 I wonder if you could also try using something like cellophane.
Cellophane from cigarette packages was used (along with the foil) to make the variable capacitor for a crystal set in an old set of instructions I saw somewhere.
I figured it miught be useable. Many plastics are good dielectrics. That's why I wondered about cellophane (like saran wrap). Cheap and VERY thin, although I don't know off hand how it stacks up to wax paper on the dielectric constant. At a guess as good or better, so between thin, flexible, and *possibly better, it makes for a smaller package with similar or equal capacitance. the actual values can be looked up in a handbook or online..