Something that has never been touched on is that so many believe Joker is the Red Hood but what if he isn't? What if he and Batman never met until he became the Joker? I think this would be a good twist especially if they just wanted to add more mystery to Joker's origins. Like a construction crew is tearing down the chemical plant where Joker became Joker and while working they discover a corpse lodged/stuck in the drain and the corpse is discovered to belong to Red Hood but at the same time there's no real difinitive evidence it is the Red Hood other than the location of discovery.
After investigating it's discovered by Batman that the same night a witness to a mob hit disapearred and he further discovers that the mob tossed said witness into the same vat of chemicals and left literally right before the Red Hood gang and Batman showed up. The reason I think this would make a good story because Batman is viewed as a dark crusader who protects the innocent so I think it would be interesting to see him react to learning that if he hadn't failed to save someone by mere minutes and that had he only been a little faster he could have saved an innocent person and prevented the creation of one of his greatest enemies.
Now I know a lot would get mad and say it would erase a pivotal moment in Batman's history but really it wouldn't. Especially if this knew origin was tied in with the Killing Joke and right after said witness went into the chemicals the mob murdered his family something else that Batman also could have prevented. I think this would be a good revelation for Batman to face especially if it was shown from Joker's or the witness's perspective via a flash back that Batman makes Gotham worse (like Batman's actions were the catalyst that led to what happened) however at the same time Batman woudn't be able to prove if this is Joker's origins because the body found in the drain would be unidentifiable and nothing conclusive could be proven basically implying said body could be the Red Hood or the witness making Joker's origins even more mysterious.
I got the idea after watching this.