There's no way people could sue them for false advertising over a story choice. That would be like suing the makers of Cabin in the Woods because it was marketed as a horror film. Their characters are ultimately theirs to define, no matter how disappointing their choice was.That would open them up to false advertising, were they said again and again that players were able to make a character that could be straight, bi, gay, lesbian or ace. I suspect the only reason that they aren't being done for that at the moment is technically the DLC is a seperate product.
The best we can hope for is that they'll be more careful in the future.