Lithgow's character (Lucas Sergeant) someone Fosse didn't like for real?

According to the Trivia section, Lucas was possibly based on Michael Bennett.

Harold Prince, prolific producer-director of musicals, including the original Broadway production of CABARET, was reportedly incensed when he saw the film. Lithgow's character often puts his glasses up on his forehead, as Prince is known to do. Prince also noted that the stage set that Lucas Sergeant tweaks in his first scene looks markedly like a set in the Prince-Sondheim PACIFIC OVERTURES (1976). There's probably a little Michael Bennett in there too. All told, Fosse allowed his most cynical paranoid fantasies to carry him away in creating the art of ALL THAT JAZZ. There is no evidence that CHICAGO's producers talked to other directors about stepping in during the four-month period while Fosse recovered from his heart attacks, just as the producers didn't pursue cancelling the show and cashing in on the insurance. It's true that Fosse harbored resentment toward producers, whom he considered natural enemies of his art; if they didn't huddle in the wings, worrying about practical concerns and money, Fosse would have had to invent them. Here he did. The enmity he felt toward Cy Feuer while making CABARET gets channeled here into the oily "Jonesy." While there's no indication that the distinguished film producer Marvin Worth was anything but supportive on LENNY (Here "The Standup"), still he gets turned into the unhinged Joshua Penn (Max Wright--years before his biggest success, playing straight man to ALF). Fosse allowed his deepest fears and fantasies free rein and creating a fictional version of his life (and death), and ALL THAT JAZZ is all the better for it.