Just make a Superman movie, then a Batman movie, then a Wonder Woman movie and then tie them all together in the Justice League movie bringing back Green Lantern and introducing The Flash.
It's not even difficult.
Why should they copy Marvel?
It gives a chance to showcase the new versions of characters as well as ones who are just now getting a movie in an environment where they get plenty of screen time and characterization so they know who is popular enough to focus on in the team and who to give the shaft and to also allow the audience to give a crap about these guys before putting them in a team movie that has to divide up the screen time between the characters.
Seriously do you really think DC should risk screwing this up becuase the characters come off as weak in the big film, instead of using the solo films to figure out who works the best and who needs a recast?