I've been thinking over this for a while now, and the conclusion I've come to is had WB planned this right from the start, and especially after the response from BvS, Wonder Woman should have been the first character in a shared universe. In hindsight this is how I would have done things:
JUN 2013: Wonder Woman
JUN 2014: Man of Steel
JUN 2015: Batman
So why this order? For starters the most exciting thing people reacted to in BvS was Wonder Woman. It's fair to assume then that a Wonder Woman solo film could have been made years ago, but WB was too hesitant to make it then.
"But why does this matter? Superman is bigger than Wonder Woman, it makes sense for him start the franchise, right? He's the most well known". Not so fast. If we also go further back a few years what did Iron Man bring to the genre? Freshness. Up until then the superhero market was essentially Batman, Superman, X-men and Spider-Man dominating to various degrees, with a smattering of lesser franchises here and there. Iron Man's succeeded in many ways but it being a totally new character well and truly would have played its part.
Wonder Woman I believe would have been the shot in the arm an infant DCEU would have needed to launch. It would have started the franchise off on a newer path, which would then be followed up by Superman 2 years later, Batman in 2016, and finally a DC Trinity movie in 2017.
"A Trinity movie? But what of Justice League?" Here's the thing with the WB, they have the advantage over Marvel in that they have three of the most famous icons in history. That means you don't need to do JL immediately. There was no real half way point for Marvel to get to Avengers, it was 4 solo films then, boom, giant team up movie, followed by a similar team up movie 3 years later. What was one of the chief issues with Age of Ultron? It felt familiar.
WB had the advantage where they could have used a Trinity film as a stepping stone to JL and increasing the number of new characters in the build up, resulting in a schedule like this:
JUN 2016: Trinity
APR 2017: Flash
NOV 2017: Wonder Woman 2
APR 2018: Aquaman
JUN 2018: Man of Steel 2
JUN 2019: Batman 2
NOV 2019: Green Lantern
JUN 2020: Justice League
It starts with a fresh face in Wonder Woman, continues with tried and true heroes in Superman and Batman with their own stories, culminating with the three meeting together for the first time 3 years later. That's the first build up to JL. You follow that up with an increase in films for new characters in Flash, Aquaman and Green Lantern mixing in with sequels for the other characters, and then hit the audience with JL after that.