2. Hugo Strange DLC
He might seem like a completely random character to focus on for a DLC campaign, but besides the leak stating WB Montreal are working on an additional Hugo Strange campaign, he's one of the only characters in the Batman mythos who knows Bruce's true identity.
This was played up as a major plot point in Arkham City, only for zero resolution when Ra's al Ghul stabbed him.
Since then, we've never known the true machinations of Strange's agency in Gotham or its underbelly, so any light shed on when he first comes into contact with Bruce - and figures out who he is - would be supremely interesting content indeed.