for justice league movie to be success like avengers, it need someone with charisma like ironman in avengers. i believe that supposed to be batman. its difficult especially with different character than dark knight actor. they should have someone play batman first to solidify him as that character before straightaway jumping in justice league movie.

or just take the easy way out, never show who the batman is even to the viewer to make him mysterious even though we will know from the credit scroll