This movie won't work for two reasons:
1.) A majority of the Justice League are just awful, boring characters.
Superman, Wonder Woman, Aquaman, and arguably Green Lantern aren't very interesting. Everyone likes the idea of Superman, but his movies are often a complete joke and overly rely on his weakness to kryptonite. Wonder Woman is just awful. Aquaman has potential if they use his ridiculous shark control powers...
But in all honesty, one good scene cannot save that guy. Green Lantern had a shot, but DC ruined that with a CGI suit and terrible storyline (no physical villain, lets have him face Parallax).
Batman, the Flash, and Martian Man Hunter would all be very cool, especially the Flash. But I just don't know how the new Batman fits into this mold, it is better if he is just left out, in my opinion. If they throw in Cyborg, that would be cool, but I don't see him making the cut.
2.) The movie needs a set up. Unless DC wants to do a 3+ hour epic, it just won't work with all the backstories that need to be made. People know about a lot of DC's characters, but they definitely need to be fleshed out. Unless people were big fans of the old WW TV show, they will have zero clue she is an amazon queen. People know Aquaman can control sea life, but not that he is the king of Atlantis. Martian Man Hunter, Flash, and Cyborg would all need backstories. Cyborg and Martian Man Hunter probably don't need their own movies, but the others do, especially Flash who can carry this movie if done right. Look back at Iron Man, he wasn't a horribly popular superhero in comparison to some of Marvel's REALLY big guys and worse of all, he was an absolute dick in the comics. But Marvel makes a movie about him starring the perfect loveable dick in RDJr and all of a sudden, he is a headliner and leads to Avengers. Flash can be that guy for DC, but they have to set it up.