You are misreading what I said. I said they'd probably want to stick to the MAIN Justice League/DC characters for the main roster this game. The ones that are easily molded into the story, because of their history together, and the ones people will recognize as fitting in. DLC is where a wider broad of DC characters could come into play, that may not fit the story they are trying to tell, but could be fun to play as.
Of course anybody can be written into anything, doesn't mean it's easy, a task they want to take on, or are even allowed to do. I'm sure DC has final say over any character they use in the end. They don't just have free reign to say "let's put Roreschach in!", as it's not their character to make that choice. If DC doesn't want V included, or don't think the story is appropriate, or whatever reason they may come up with, then it's not going to happen.
I'm not against the character, i'm just being realistic here. Judging by the roster we have so far, the story at hand, and the title of the game, obviously The Justice League is the main focus at hand, so the likes of Swamp Thing, Animal Man, V, Roreschach etc. The characters that aren't usually tied in with the main DC events, aren't likely to be featured in the main story or roster.
That's just how I see it. Not impossible, just highly improbable.
With that said, i've been wanting Swamp Thing from the start, but I accept that he'd likely be DLC if included at all.