Second John Travolta.
This sounds like a dumb movie that doesn't need to be made. If Cage doesn't want to do it, then change the role to some fictional celebrity.
That one guy from the Big Bang Theory - not the Indian, or Sheldon, or the main character - actually does a FANTASTIC impression of Nic Cage. Busted it out on Conan one night. He should be Nic Cage in this movie.
EDIT: Simon Helberg. Here's the clip. He can also do Billy Baldwin, apparently :)
Hunting for a decent shonen show to watch? Sam says look no further... and grab a drink, this is good