Not sure how Superman, Aquaman, Green Lantern and others would be able to work with the same tone. The Batman and Joker are both incredibly grounded films because the respective characters aren't actual superheroes. Start throwing in alien demigod powers, talking to fish, being able to conjure magic etc. and that doesn't really work.
Or maybe it could, but I could not envision any of those characters in Matt Reeve's film.