On the stream aired today they showed off some battles from which I found two things to be worth pointing out:
1) There can be multiple of the same characters in battle
I mean, thinking about it now, it makes sense because there would be clashes between people wanting to use the same character. Some people prefer to play with their favorite character and they won't settle for anything less so this feature had to be in. Still! 6 Sephiroths? 6 Shantottos? That's insane.
2) There's one summon per team and the summoning is a big deal
The animation and the presence of a summoned beast itself is epic. Not the FFXV-scale epic, but pretty big anyway.