pvp3 - for people with 20k score each, higher cost to play, higher reward (electrum)
upgrades - how about a 2nd option when upgrading a card, like the original upgrade for 1500, then another upgrade for 2500, like, blackhole upgrades to blackhole or gravity well, gravity well could drain all quanta from the enemy matching their mark, and gain life equal to it. so similar to black hole, but different.
obviously more quests would be nice : )
gods - since we have false gods, why not full blown gods, maybe that have NEW rares that are only obtainable from them, and possibly limit the number of god matches per day to like 5.