I think I would exchange Jeunet before changning the writer. Seeing how Jeunet browned everything (and well, he matched the color tone of the movie to its quality - yellow and brown...). Jeunet approved the Pumpkinheads that ADI brought him, approved the eyes in newborn, shot the aliens in lightened environment, okayed the Loony Toones humor etc
I think a great director can make a great movie even from a so so script. Alien is an example, the script was virtually the exact same story that pulps and cheap B movies had multiple times before Alien, yet the approach, the look, the feel, the designs , the characters and the performances and art direction made all the difference