Jack Sparrow is such a unique character that trying to replace him with somebody else, or trying to add him to an existing idea that he wasn’t originally part of, seems like a herculean task.
Honestly, I’m not even sure how you work on developing a new Pirates of the Caribbean movie without answering the Johnny Depp question first.
A movie with Jack Sparrow is a sequel to the existing franchise, a movie without him is a reboot that takes the brand in a new direction.
It would seem like you’re looking at making a very different movie with or without him in it.