Nobody is talking about, what they property are doing with the Joker? For me it looks like, Jeremy unintentionaly created a sub-culture in Gotham, which speaks to a lot to anachist, free-spirits and broken people (the show present it as a mix between Gothic and Punk). The scene will properly grow overtime and I can actually see them, dismissing Jermey, if he would be coming back (many groups distance them self from there creators or inspiration, since living people can make for bad symbols).
The Joker would become an embodyment of this sub-culture. One random guy, who takes everything to far. Almost like all those people are summoning an demon or god. It kind of explains, why people would still support the Joker. He is created through the people of Gotham.
This would also give the producer the chance to involve the Joker without actually using the character. Like with last episode they can create people, who represent a fraction of him out of this sub-culture. All the small bits, which leave a mark on Gotham and all will life on as a part of the Joker in the future.