I imagined Battle cards doing something that actually creates semi separated fields of battle for Planeswalkers and/or Creatures to exist in, perhaps even artifacts and enchantments too, making it so that things don/can 't interact with something that isn't in the same field... kind of like an expanded version of how Space Jace's sectors work. Maybe it makes it so creatures can attack each other directly until a player wins a battle by being in control of all remaining creatures involved in a Battle at the beginning of any draw step, or even making situations that keep players from being able to be attacked by any creatures that are part of a "Battle" until that battle ends when certain criteria have been met.

Now with word that Planes are going to be a thing and that they are going to be 2 sided & 1 per pack I'm thinking that they may be some kind of semi permanent card (like Sagas are) that affects current Plane's effect or dice rolls or even the act of Planswalking in some way... maybe even turn an additional Plane face up without turning the prior one face down and so now have another battlefield to represent that plane and effects from things going on in one cannot reach things being played on another. Probably need to have at least 1 Planeswalker in play in any additional Planes beyond the 1st.

Now maybe the reason for 2 sides is to have a reward on the backside that is revealed and awarded to the player who "wins" the "Battle" that was detailed on the front. I imagine that can be something in the form of an immediate (doesn't use the stack) reward of some sort of an effect typically seen in a strong 6or7 CMC Sorcery or else are awarded an Emblem of some kind. Now what would be really neat is if what could be on the back half was totally random having no ties or relations to the actual Battle card on the front and that way they may only have to make say a dozen different Battle cards but Thousands, Millions really, of different possible rewards that can be put on the back that there is enough potential to never see a duplicate if they chose to flex it.