>>47306
>[…] settings for cannibal world stories […]

>- Population imbalance […]
This one is so good - or should I say obvious/popular - that there is already a bunch of stories.

>- Recreationnal cannibalism. […]
While in (text) stories not that often to be found as the first theme, this setting was used in many movies. Think of
"La decima vittima" ("The tenth victim", Italy/France, 1965),
"Das Millionenspiel" ("The Million Game", West Germany, 1970),
"Rollerball" (United Kingdom/Canada/United States of America, 1975 and its remake United States of America/Germany/Japan/Canada, 2002),
"Le prix du danger" ("The price of peril", France/Yugoslavia, 1983),
"The Running Man" (United States of America, 1987),
the "Hunger Games"-movies (United States of America, 2012 and 2013; United States of America/Canada/France, 2014; United States of America/Germany/Canada/France, 2015; United States of America, 2023 (announced))
and not to forget the "Purge"-series.
Yves Boisset, director of "Le prix du danger", sued Twentieth Century Fox for copying because the screenplay of "The Running Man" matched that of his own film. "The Running Man" is very loosely based on the novel with the same name by Richard Bachman, better known as Stephen King. Although the book is completely different from the movie, it has the same mechanic as the book "The Prize of Peril" by Robert Sheckley, from which "Das Millionenspiel" and "Le prix du danger" are adapted. Sheckley also wrote "The Seventh Victim" back in 1953, the original for "La decima vittima". It seems that even this theme offers only a small room for variations.

>[…] overpopulation theme, a world where there's not enough food to go around. […]
To this reason not only applies the same as to the former points, it is - as I said in >>47305 - the most unrealistic.
Fun fact: In 1973 (fifty years ago!) Charlton Heston and Edward G. Robinson starred in Soylent Green, where overpopulation, euthanasia and the recycling of the corpses are the subject.
Special fun fact: The movie's action took place in 2022.

BUT, having said all this: I don't want to discourage you and/or stop you from writing. Create a good story - hopefully with some action and erotic - and I will happily read it, in particular if you took my name into account. ;)