I will just be happy when I hear that Dr. Manhattan isn't playing legos with the DC Universe. Sometimes it feels like he played around with other universes though (JLA: Act of God). Although I have wondered if it's in DC's nature to do Ultimate DC, New 52 sort of felt like Ultimate Marvel in some ways (altered characters and history). Also, maybe, just maybe, N52SM gets reincarnated into Earth-22.
Plus, since you mentioned a "Fallout" world, that's essentially the fanfiction/fanart idea I am working on now, with Wasteland Warrior. Basically, Kal-El landed shortly before nuclear war happened, and he ends up growing up in a wasteland, using his amazing powers to first defend the Kents and New Smallville, then later moving on to helping people with excavation of the ruined Metropolis. Crazy ideas, but hey, that's just me, and I really liked the Fallout games.