9 Films DC Should Make Before Flashpoint
3. Legion Of Doom
While, generally speaking, villain team-up films haven't exactly been a recipe for success for DC in the past, this is a film that could be used to great effect.
To coincide with Flashpoint, several tie-in mini-series were published to chronicle the fate of several characters who appeared only briefly in the main storyline. One such of these spin-off series was focused on the fate of the villains themselves. While several classic villainous characters played integral roles in the main story, such as Deathstroke, Sonar, Icicle, Clayface, and Captain Cold, multiple others' stories were told in the pages of this tie-in series.
In giving audiences a Legion of Doom film, DC could properly build up this roster of core villains, so as to have them all fully assembled and fleshed-out in the primary timeline beforehand. This would ensure that audiences were aware of these characters and their villainous nature.
Without a film in which these characters could be well-established, audiences would be left in the dark, which would lead to only greater confusion if the characters were to be used in the primary timeline in later films. Save everyone the headache, DC. Besides, there's no way you can mess this up as bad as Suicide Squad, right?