Why would or should Maul be the Vader? What does that add to the PT and why should it copy the OT in that way?
Maybe motivation for the main characters and also someone the audience can attach to? Basic stuff you need for a movie to work, even more necessary for a trilogy.
I dont know how you can think any of this when Maul killed Kenobi’s master, as if that isnt a strong enough reason to keep him as the main villain.