Swamp Thing, Zatanna, Etrigan The Demon, John Constantine, The Spectre, Deadman-- you put all these guys in one movie and my horror loving head is bound to explode. Nevertheless, Guillermo del Toro is making plans to do just that on behalf of DC and Warner Bros with DARK UNIVERSE.
DARK UNIVERSE (currently the film's working title) is among the zillions of projects del Toro is currently developing, but it sounds like one he may just see through-- if not as a director, then in a producer-ly capacity. Apparently he has already submitted an outline for DARK UNIVERSE and has selected a writer for the film (though he's staying relatively hush-hush about the identity of said scribe).
Del Toro goes into more detail in the video below, which, if you enjoy any of these characters, is well worth the watch. Honestly, I could listen to del Toro talk about anything, but hearing him pontificate on the development of DARK UNIVERSE and the greater DC Comics film franchise in general is nothing less than captivating. Check it out below.