Shane Stevens' The Warriors...?
It appears that long before the project went to Walter Hill, Shane Stevens was hired to adapt Sol Yurick's The Warriors into a screenplay. Yurick's novel was written in 1965. Hill's film version was released in 1979. But Hollywood was trying to make a film version as far back as 1969.
From The Movie Call Sheet column of The Los Angeles Times, April 25, 1969:
American International has signed Shane Stevens to work on the screenplay of "The Warriors," based on the book by Sol Yurick. Robert Fresco and Denis Sanders will produce with Sanders scheduled to direct.
How different would the movie have been with a screenplay by Shane Stevens and direction by Denis Sanders?