Great ideas and comments, i saw this movie on wednesday night and enjoyed the movie - great acting and a great city/world.
At the end, on the police car, bloodied lips and soaking int he applause was beautiful and god knows how much i wanted Batman to be in that scene - but it totally worked for his rebirth as the batman was born.
This sequel, if it had to be done, has to totally stay away from mainstream DC, it just wouldn't work with the tone it's now set.
However, i felt MOS fit that world beautifully and it's a damn shame, in my opinion Snyder couldn't have delivered his version the same way Phillips did, MOS felt incomplete. Anyways.
My idea for a sequel - focuses on a Gotham Joker left behind - the riots, it gains traction, the shocking murder of the talk show host Franklin is on everyones lips and Bruce is almost elevated as a poster boy of what is wrong with the city, he's the biggest victim - everyone wants a piece of him, Alfred keeps him secluded away so he doesn't realise.
Joker sees what he has created and misses the stage, his fans call for him and write to him, he doesn't get it or allowed access but it gets through to him. He also sees people coming in to arkham, just to see him, he also meets Dr Harleen F Quinzel, who is just a straight up therapist - i would have someone like Gillian Anderson play her. This starts an obsession with her, similar to Sophie. He fantasizes over her and sketches her sexually in his book, and on the walls.
As a side story it still torments Bruce, not only the murder, but why it happened - that creepy weird guy, who put his fingers in his mouth, he can taste him still, the guy who caused it all - as the batman idea gets stronger over the years, so does his hatred for the joker. He hates how he is infamous in his city - he has to get away.
So we skip years after each act - second act it's been 10 years, Arthur is still in Arkham, the media mention Bruce Wayne has departed on his travels - obviously this triggers Arthur - the sense that Bruce is off enjoying life whilst he is inside, confused, tormented by it all.
Dr Harleen is still working on him, but we see they have a more relaxed friendship, almost like she is family visiting him (or do they?). He opens up more about Bruce, Thomas Wayne's words - how people hide behind a mask are cowards, they're jokes, jokers. He imagines Bruce curled up in a ball, nightmares of the joker, a devil with horns and a cloak, this is inter cut with Bruce out in the world trying to find his place.
One flew over the cuckoos nest would be great inspiration for the second act which itself is spread over 5 years - then it's the 15th anniversary of that night.
Final third - word is out that a batman is in town, cleaning up gotham and it's thugs - Arthur tells Dr Harleen what he has heard - a man bat, hiding behind a mask, the bat signal each night in the sky, visible from his cell.
A riot occurs, batman is coming in for the joker, we see shadows, capes, graple guns.. Joker manages to evade and is out in the court yard - he turns and sees Harleen holding the keys, she beckons him over and he escapes, as the batman can only watch on as the media and mobs zone in.
The next day, as gordon looks through the cells and the mess, he finds Arthur, curled up in a corner, surrounded by imagery of bats, batman, a flash light with a bat toy over the lens, on the wall, notes - verses of bruce waynes life and travels...
Batman never existed, it was all in Arthur's mind.
You can totally see how he would create a fantasy to equal his pain and that bruce would be the perfect foil. Wasting away inside arkham, it's the perfect fantasy.
However... a good post title sequence if they wanted, would be that night... arthur is restrained and quietly staring at the night sky and the bat signal appears - arthur breaks out that harrowing laugh once more.
Did it or didn't it happen...