Justice League: 10 Ways Deathstroke Could Appear In The DCEU
5. He's In A Flashback/Vision/Dream
What does the DCEU love doing more than cramming as many iconic comic book plots into a single movie regardless of narrative suitability? Why it's flashbacks! Batman V Superman was chock full of shock dream reveals - young Bruce in the batcave, Bruce in the family crypt, the Knightmare, Flash's visit, Superman meeting Pa Kent - and Suicide Squad was even more brazen, with a first act made up a garishly cut recaps and Harley's origin coming out of nowhere.
So it's reasonable to expect that Justice League will have at least a couple (I 100% bet there'll be one of Apokolips), and if the film is going to hinge on Batman - he's the most popular thing to come out of Dawn Of Justice and, in bringing the team together, is the de facto lead - it'd be likely he'll have some internal conflict showcased. Deathstroke is a perfect way to do this, highlighting how the threats the Dark Knight's gone up against have changed over the years.
The big thing working against this idea is that Slade appears to be in the Justice League's ship, although since when have the DCEU's visions had to make sense?