pujimaki
Why not both superhero universes? There’s no reason he can’t film The Dark Knight Trilogy and then go on to film Iron Man, The Avengers, etc. If he’s successful enough and get want him as director, they’ll move the release dates to work around his schedule. Sadly, if he wants to make big money, he will have to rely on big budget films, but there’s no reason he can’t crank out art films as well. Look at Christopher Nolan’s career. Memento, Inception, etc. actually, that’s a good opportunity: you should have him write Memento and direct it.
Option 3 sounds very interesting, but I don't think you should do it the same as mcu. Rather, make it subtle that the movies exist in the same world, and a big collaboration and character interactions should be done differently than the avengers/justice league. It doesn't make sense for them do do that, especially since most of the characters are lone wolves