Maybe they could reboot the old series and make this new dystopian end of the world world its own universe and continue to show the rebirth of civilisation etc and continue the adventures of our heroes, but still show events before flashpoint.
Sorry man, this idea got a bit too pretentious and unrealistic for me to enjoy. If you have too many superhero movies at once the hype dissipates and they will not be box office successes. which is not what DC or Warner wants. Also DC wouldn't pay you unless you came up with original story ideas. None-the-less i respect your ambition :)