How awesome it would have been if AR URF was released just like normal but with the Snow Rift, and snowball summoner spell.
Being able to flex your honor 5 in game like a mastery, and not just a ward. Remember those cool summoner icons that activated after a take-down, re release them. Probably just nerf ZZ rot and banner of command for this game mode, I can already see it being anti fun. That's all I can really think of at the moment. I noticed Ultimate hat was removed. Kassadin will be pretty weak.