From what I gather from the few interviews so far, it seems like the Paradigm Shift system will make a return in some form or capacity. If you can preset costumes/armor pieces for Lightning like it has been stated, then this is a possibility to create a Paradigm Deck for battle. It has also been said that you can change costumes during battle and that you can make Lightning either 'all out offensive' or defensive.
Maybe you have a pool of abilities for each costume (or to cover the basic roles/spells in general) and you assign which you want to the face buttons for battle. Maybe you can even mix and match them to have like an offensive healer type...a COM with the ability to heal.
It looks like they could take this battle system into a whole lot of new and interesting directions. And we could create interesting combinations and not be limited to singular role abilities at a time like we were in the past games.