Keep Nolan's style of serious and dark storytelling but don't make it too realistic. The action scenes should be more "superheroic". Make Batman jump and kick more and more agile than the previous ones.
1st Film: Start with "Year One" which covers the origin and training in 5-10 mins thru flashback. Then adapt the story of "Batman: Prey" for the second half. So, Hugo Strange would be the main villain. Use Penguin in place of Carmine Falcone as the secondary villain and Deadshot in place of Night Scourge as the henchman. Deadshot would provide some hardcore action sequences with lots of bullets and bombs. Deadshot would keep the comic book feel while HS would maintain the dark Nolan approach.
Batman/Superman: Since this is a "DC Cinematic Universe", this movie is bound to happen. We will Batman against Poison Ivy who would try to control Supes like she did in Hush. In the end she would be revealed to be working for Lex Luthor. The film would focus on the strained relationship between Bats and Supes. Their 1st encounter could be a fight.
2nd Film: The Riddler is the main villain - a crazy genius determined to prove his superior intellect. Trying to solve his riddles would lead Batman to encounters with other villains like Killer Croc and Catwoman.
3rd Film: Best villain for a third film would be none other than the Joker himself. He would be introduced in the previous films and in this one's beginning, he's locked up in arkham when harley quinn would free him. "The Man Who Laughs" would provide an interesting story and would feature the Joker venom. Also, "The Killing Joke" would be incorporated with the joker paralyzing Barbara Gordon. So, she would become Oracle and help batman in tracking him down. And since I'm talking of a shared universe, oracle could be used in future JLA films or a "Birds of Prey" movie. Harley Quinn would be Arkham City style, providing some action scenes.