Ok, I have been thinking about this for a while, and I have decided that Arrow, and The Flash ,from the CW's series, need to be involved with the Justice League movies.
So, we all know that Batman VS. Superman is just a big pickup to the Justice league. So, what about all of the other members? Wonder Woman, Superman, and Batman are all obviously shown in the Batman VS. Superman trailer, but unless they introduce the other members of the league in the film, they will have a very quick introduction!
Now, I know that the Green Arrow isn't part of the justice league in some story lines, but the Flash is. What if, instead of making an all new character, DC just used the one they already have RIGHT IN FRONT OF THEM? They need to use the CW's Flash, so their movie doesn't introduce an unknown brand new character! Plus, I think Most people would like to see CW's Flash in the Justice League.
Green Arrow would also be a great introduction into the league. All I have to say is....WHY NOT? Use the characters you already have, and give us fans more story, and action time!