@Fragrance: I'm still working on ways for planeswalkers to tap into mana... thinking about small areas of the battlefield changing form to represent places they've visited, such as an water feature or lake spontaneously forming to represent an Island... Not sure how that'll work on a larger scale, though; also, what happens once the battle is over. Do they just poof out of existence? *shrug*
Alternatively I could pull the mana-generation mechanic from MtG Tactics and have the planeswalkers suffused with more mana with which to cast as the fight progresses... but then, Tactics was a terrible game. No matter which way I look at it, mana alone provides a fair bit to work on. Also gonna have to determine rules of a fight; we can't have someone casting an Eldrazi Titan on turn one. But then, the Titans are banned from characters' spell lists anyway. Just making a point.
Edit: I just learned some brilliant stuff about Innistrad. There'll be a planeswalker with five loyalty abilities, and new versions of Garruk and Liliana. Also, red-aligned vampires... a bit of an oddity.