Don't Let the Fall of America be Your Fall
I was actually thinking this too. Plus, this could be a good way to introduce Tim Drake as well.I think Gyllenhaal could be a good Batman but i rather Ben be given a chance to do a few movies and pass the torch to Nightwing than constantly recasting Bruce.
Dick Grayson being batman feels like a natural conclusion/next step to his arc and allows DC something marvel cant do as easily.
The way I see it;
Batman movie 1: More or less a detective, noir, action thriller.
Batman movie 2: Knightfall event pt.1
Batman movie 3: Knightfall event pt.2 (In which Ben passes the torch to the actor of Nightwing to be batman for the DCEU)