Beyond those three, its anyones guess, but Ive been through the list of available mechanics and keywords to pick out what seems the most likely: Battlecry A Go Wide strategy is likely given the huge armies and battles in the series, and battlecry is a way to help break stalemates
AKROMAS WILL White has way fewer finishers than other colors, and the last hurdle for it to truly succeed as a color is to give it more ways to turn the corner and convert a board into a win
Planeswalkers with good board control options and high loyalty counts are hard to deal with, much more so than cards like Elesh Norn or Griselbrand
Nothing at a low mana cost though, like blue, red, and even green have been getting
That means she reduces any damage being dealt to her by 1 point per Knight you have on your side, which surely means were going to see some Knight-focused decks in the meta, taking advantage of this excellent ability
4 Professor Oak Pot Of Greed When your deck already consists of only 20 cards, the ability to draw two is beyond valuable