Oh man! I would be OK with that but i don't believe Affleck will do it. He's in my top 3 or top 5 for directing it but not my main choice. To me the logical thing for WB to do is ask Ben first, and ill bet anything he declines due to other projects. The next choice is probably David Ayer since he's building so much of this Gotham City. Half a dozen Bat-related characters will be written by and directed by Ayer (Joker, Harley, Deadshot, Deathstroke, Hugo Strange, Killer Croc, Arkham Asylum). So this would depend on the success of Suicide Squad. The third choice could be anybody and so i vote Denis Villeneuve. He's on a roll, he's incredible, he's moving into sci-fi territory by directing a film with Amy Adams next year as well as Bladerunner 2 the year after.
Others on the shortlist could be Rian Johnson (Looper, Star Wars Episode VIII), Chad Stahelski and David Leitch who did John Wick (imagine the fight choreography and look).