7) The Comic Has A Complicated Backstory That (Probably) Won’t Make It To The Films
It’s fair to say that the backstory in Gotham City Sirens won’t make it to the feature film. The reason? Batman is currently dead in the comics.
Sirens began after the Batman R.I.P arc, in which Bruce Wayne perished. At the time of the comic, former Robin/Nightwing Dick Grayson has taken up the mantle of his mentor, in attempt to convince the criminals of Gotham that the Bat still lives. Selina is the one largely affected by this as she’s had her heart broken by Bruce’s death and knows that this isn’t the Batman she knew and loved.
Selina also begins the series at a weak point, seeing as she had just had her heart cut out by Hush in the appropriately titled Heart of Hush arc. Thankfully, she was magically healed by Zatanna and was fine again. Because, comics.