They could also contrast the censorship between different cultures and countries, ie japan with it's Guinea Pig films and Men behind the sun,etc and the fact that a lot of the films we're finally seeing uncut in the u.k(well almost) have been available worldwide for many years ie Cannibal Holocaust.
Also how in America films can be released unrated unlike our censors who charge so much for extra's and are running small releasing companies into the ground by forcing them to release substandard products in terms of extras. How digital is replacing actual hands on copies even though a lot of these digital copies are substandard and costs are preventing restoration and archiving of cult films.
I know that covers a lot of ground but i'm sure one more documentary could be constructed from these elements.
And like i said there is still so many bizarre and controversial trailers for trash/sleaze masterpieces that haven't been covered yet.
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MIKE: I've got it! Peter Cushing! We've got to drive a stake through his heart!
VYVYAN: Great! I'll get the car!
NEIL: I'll get a cushion.