It seems to me that the "DC Universe" is not nearly as efficient as those people who are churning out Marvel characters . . .
I think that the only thing that can save DC is if they have been secretly making two films in BvS. I mean, all those new superhero and villain characters (including a new Alfred and Commissioner Gordon) need at least some kind of introduction, and then we need time to gape at a new batmobile, batplane, B's alternative armor, etc.
The producers did this with Three Musketeers and Four Musketeers many years ago, and I believe (correct me if I am wrong) that Superman I and II were made for the most part at the same time . . . then they finally decided to ditch Donner's version of II and install Richard Lester as director.
There was a bit of problem with the deception in making Musketeers 1 and 2, so the producers would need to sort out the contracts of some of the characters and staff. Very few people would know that more than one film is being made or somehow the cat would get out of the bag!