Agreed. It's not necessary that every single hero gets a solo movie, however it is very necessary that in the unifying movie, there's enough space for each character... something that seems very difficult to achieve if you throw in so many super heroes like BvS is "accused" of doing. So far only Cyborg is confirmed, however with such a marginal character already being confirmed, I have no doubt that they will shoehorn a bunch of more important guys into this...
Still, can't help but feeling hyped for this, simply because of Batman meeting Superman, as long as that part of the story works, I'm happy.