I'd like to see the idea that, just as Batman has inspired citizens in Gotham, the Joker has, as well. Not copycats, after all, there's no substitute for the Joker (which, undoubtedly, is all the Jokerz gang would be. "We didn't want to recast the role, so here's the next best thing!"), but bumping up the criminal element to a new leverl. Freaks start oozing out of the woodwork.
That's something I thought was very clever about the way they wrote the Riddler in Batman Forever. He was fascinated by Two-Face, and decided he wanted to follow in his footseps.
That's a concept I'd like to see carried over into the new series.