You can’t really ‘remake’ a Sergio Leone film. That’s impossible. Its like remaking a Kubrick film, or a Hitchcock film... It really can’t be done.
The Birds 2... or Dr. Strangelove the sequel... It’s not going to happen.
Here is a pitch for The Graduate Part 2 in the movie The Player.
https://m.youtube.com/watch?v=biaTRgFKJ3I