Bringing Nolan and co. on board is the only way for anything like this to work for Warner Bros. Nolan's Batman films have grossed well over $2 billion worldwide and who knows how much more via home video.
And you can darn near take it to the bank that it's going to be a Batman/Superman film, not a full-blown JL movie. There's no way this Batman won't look silly in a live-action film punching aliens in the face, blasting off into space, and fighting alongside superpowered beings.
As far as Superman, Nolan co-wrote the story for MAN OF STEEL and is producing that film. It, like his Batman films, are going with the "realistic" tone. The premise is what if the human-looking alien that can fly and is almost invincible REALLY showed up in OUR world. I'm worried, but if anyone can make this particular Batman and Superman work on film it's Nolan, David Goyer, and Zack Snyder.