How could you make Wonder Woman, an Amazonian princess with incredible abilities and a rich history all her own based in a cool world of Greek myth, clearly subservient to the male superheroes in Batman vs Superman? By making her Supergirl, more or less, a Kryptonian whose power levels are lower than Superman's.
That, according to Batman On Film, is the approach being taken with Wonder Woman in Batman (Also Featuring Some Superman Content). According to the site it will be revealed that the Amazons - an all-female tribe hidden from the World of Man - are actually descendents of the Kryptonian outpost on Earth that Superman discovered in Man of Steel. Using Kryptonian genetic engineering they have made themselves an all-female society. But since they've been on Earth for millenia they have become more adjusted to our gravity and atmosphere, making them weaker than a newbie like Kal-El.
First, take this with the old grain of salt. Batman on Film is reporting other stuff about Batman vs Superman that directly contradicts what I've heard from strong, strong sources close to the movie. That said, this sounds exactly like the kind of nonsense I expect from Warner Bros when it comes to dishonoring their DC characters.
Not only does this make Wonder Woman just a subordinate to Superman, it robs Superman of his whole identity - the Last Son of Krypton. The whole point of the end of Man of Steel was Superman making a choice, that Krypton had its chance... but now there's a whole civilization of Kryptonians just fucking about on Earth. One of the big mandates of Crisis On Infinite Earths was to return Superman to a status quo where he was special; by the 80s he was surrounded by a dozen surviving Kryptonians, to say nothing of the whole Bottle City of Kandor. That was a smart move - as the template for the modern superhero Superman has been cannibalized by so many characters that he needs something to set him apart, and his uniqueness in the universe is just that. Removing his uniqueness removes much of what makes Superman a special character.
And making Wonder Woman simply a depowered Superman is offensive. She isn't allowed to stand on her own but must be in some way defined by Superman. It's crazy.
Above all, it's creative cowardice. While Marvel gets cosmic and weird Warner Bros seems to want to make everything insular, connected to one small idea. All super powers come from Krypton! They don't have to explain anything! There are no more audience buy-ins! You've accepted Krypton? Well, here's Kryptonian tech and surviving Kryptonians and Kryptonian monsters (likely the explanation for Greek mythological beasties). It's infuriating - the world of superhero comics is one of expansive imagination, and the beauty of multiple franchises (like Marvel has) is that each gets to live in its own world. You can have magic and you can have spies and you can have street level heroes, because they all only come together every now and again.
I don't even know that I believe this rumor, but it seems just stupid enough and just 'neat and tidy' enough to come from the people who think 'realistic' is the best way to approach superheroes. Like I said, some other stuff BOF is reporting lately has been privately contradicted, so I'm hoping this is just wild specualtion souped up to read like insider info.