Currently how the time line is, we can't have a Future Earth DLC based on the opening cinematic because that timeline no longer exists for our world. Future Lex rewrote history when he detonated the exobytes in the atmosphere. If we were to travel to an alternate time line sure but our future isn't so bleak anymore.
Sounds like a good idea like have it just before Brainiac comes, you know the build up to the opening cinematic.
The ELSEWORLDS? DLC? That would be neat. Never did follow those comics. Yet gives breathing room from the CANON that is DC to solve issues we all feel are there. If we have the powers of these heroes did these heroes really need to stay being heroes and so forth. I agree ELSEWORLD DLC would give us a chance of creating our own story. And more CINEMATICS. Not storyboard slideshows.
Or how the powers that be are dealing with the majority of Earth's population turning metahuman due to exobit exposure. Both hero and villain alike. Maybe the introduction of Amanda Waller and Suicide Squad? Somebody.