Originally Posted by
bat39
I don't think it should be too much of a problem. 'The Flashpoint Paradox' worked well as a standalone, so I see no reason why a Flashpoint movie can't. There's some degree of familiarity with the characters and the universe already among wider audiences, and movies like Star Trek and X-men DOFP have done a good job acquainting people with the concept of time-travel and parallel universes. Hell after 'Avengers Endgame' people will probably be a LOT more acquainted with those concepts!
The first half-hour or so could set-up the story by reintroducing Barry Allen, giving a quick recap of the pertinent parts of his origin (the accident which gave him his powers, his mother's murder and dad's wrongful imprisonment). Maybe throw in a mention of his having become famous helping a bunch of heroes stop an alien invasion. This part can introduce Iris West and Barry's budding romance with her. Maybe the Flash takes down the Central City Rogues in an opening action sequence. And Cyborg can show up early on in a cameo, along with Silas Stone at STAR Labs, who's helping Barry measure the true extent of his speed and theorizing that he might be capable of time travel. Barry visits his mom's grave on her anniversary, is haunted by memories of the night of her murder and vague visions of a man in yellow, and then starts running very fast.
Cut to the Flashpoint timeline. Barry has no powers but his parents are alive and well. Aquaman and Wonder Woman are at war. Cyborg is the leading superhero. And we have Flashpoint Batman of course, whom Barry teams up with. Once Barry recreates the accident that gave him his powers, he encounters the mysterious man in yellow at various points in the movie who taunts him, and he knows that that man was responsible for his mother's death in the original timeline. So the movie has two major plots - one is the wider plot about Flashpoint and the efforts to stop the war between Amazons and Atlanteans from destroying the world, and the other is Barry learning about Eobard Thawne and remembering gradually that his own attempts to save his mother's life when he time-traveled is what shattered time.
The movie ends with Barry fixing things of course. And we can have him visiting the Batcave to give Thomas' letter to Bruce, with Bruce this time being played by the new actor from the Matt Reeves' film.
If the animated movie managed all this in less than 90 minutes, then I'm sure a 120-150 minute live-action film, if well-scripted can manage all that.