Warning everything below is speculation.
With the acknowledgement that Cyborg will appear in Batman vs Superman, I began to wonder how he would be introduced. Then I was replying to a post about Arrow, and in the middle of writing I had an epiphany: [Batman vs. Superman](movie:711870) will be the origin story of Cyborg.
Now follow me here.
Traditionally there are seven members of the Justice League, Superman, Wonder Woman, Batman, Flash, Green Lantern, Green Arrow and Cyborg. Now of those seven only two of them would not have appeared on a screen big or small by the time MOS2 hits the big screen, Wonder Woman and Cyborg. (Note: I am swapping Aquaman for Green Arrow)
Just so we are clear I am counting Green Lantern's movie as it sets up the basis of the Corps. I also don't think its in need of a classical reboot but jump a head to John's Lantern.
Cyborg could easily be made into a villain, remote controlled by Luther isn't to far out of the realm of possibility. Start the movie before the Kryptonian attack and have Vic fall victim to the gravitation pulse that tried to terra form the Earth. He's found at Star Labs with "metal" fragments all over him. They rush him to MetGen and start trying to save him, when we find out that its actually nano tech that is assimilating Vic and whatever tech is near by. Luthor is smart enough to hijack Vic making him the villain in this movie. Only in the end to be saved by Superman and Batman, with Wonder Woman flying in last minute.
I can hear you saying, "pssh your crazy, Wonder Woman needs an origin story!!", and I agree but she deserves her own movie, and the great thing about movie is you can time travel in them, after she appears in MOS2 they can go back and do her origin. However I think they biggest problem with a Wonder Woman movie is her origin there haven't been to many successful Greek mythology movies made, and she is very heavy on the Greek mythos.
Do you think my epiphany is crazy or is it something you have heard before?