This reminds me a heck of a lot of an old roleplay that, sadly, died down after a little while. The story was that random portals started popping up all over, sending people from DC to Marvel and vice versa. After a while they were able to be controlled, and most had the ability to travel freely. Once, Darksied and Thanos were both trying to escape through a portal at the same time, and Iron Man and Shazam shot the portal at the same time, fusing the two villains. DarkThanos then slammed the two universes together, and ruled over them, klling all who got in his way, but not directly interfering much other than that.
It was a cool roleplay, but we never actually got to even interact with DarkThanos. If you want to bum off his origin and create another story like that, I'd be fine with it.
Also, yeah, I'm interested.