My go-to example why it wouldn’t work is the scene in the Batman where he can’t even glide off a building without smacking into a car and nearly dying. This Batman is “grounded” and “realistic” to such an extreme degree that he could never keep up with superpowered people in a team-up movie. Also his Batmobile is just a muscle car he modified. This guy could never have a bat-jet or a sub. What’s he gonna do in an alien invasion LOL. You’d have to change everything about him to fit the DCU.